| Cyclotron Limited | Private company limited by shares | Live |
| HONG KONG CYCLOTRON LABORATORIES LIMITED | Private company limited by shares | Live |
| FIRST ORIENTAL CYCLOTRON LIMITED | Private company limited by shares | Live |
| CYCM (Hong Kong) Limited | Private company limited by shares | Live |
| CYCMAX SCIENCE COMPANY LIMITED | Private company limited by shares | Live |
| CYCO LIMITED | Private company limited by shares | Dissolved |
| CYCOM LIMITED | Private company limited by shares | Dissolved |
| Cycom Hong Kong Limited | Private company limited by shares | Live |
| CYCOM TECH LIMITED | Private company limited by shares | Dissolved |
| CYCOM TECHNOLOGY LIMITED | Private company limited by shares | Dissolved |
| CYCOMTECH ASIA LIMITED | Private company limited by shares | Dissolved |
| CYCON INDUSTRIAL CO., LIMITED | Private company limited by shares | Live |
| CyCon Technology Limited | Private company limited by shares | Live |
| CYCONIA COMPANY LIMITED | Private company limited by shares | Live |
| Cycoviz Limited | | Live |
| HK Cyctech Co., Limited | Private company limited by shares | Live |
| CYCTECH (HK) LIMITED | Private company limited by shares | Live |
| CYCTECH INVESTMENT LIMITED | Private company limited by shares | Dissolved |
| CYDA MOTORIC INC LIMITED | Private company limited by shares | Live |
| CYDCOR LIMITED | Private company limited by shares | Live |
| CYDCORP LIMITED | Private company limited by shares | Live |
| CYDD COMPANY LIMITED | Private company limited by shares | Live |
| Cydecorp Limited | Company limited by guarantee | Dissolved |
| CYDEL (HONG KONG) LIMITED | Private company limited by shares | Dissolved |
| Cydemco Trading Pte Limited | Private company limited by shares | Dissolved |
| Cyder Limited | Private company limited by shares | Live |
| Cydiax Pvt Limited | Private company limited by shares | Live |
| Cydonia Limited | Private company limited by shares | Live |
| CYDOT COMMUNICATIONS MANAGEMENT AND TECHNOLOGY LIMITED | Private company limited by shares | Dissolved |
| CYDR LIMITED | Private company limited by shares | Live |
| CYEBA LIMITED | | Live |
| LYEE CYEE LIMITED | | Live |
| CYEFFER LIMITED | | Live |
| CYES INDUSTRIAL (HK) CO., LIMITED | Private company limited by shares | Live |
| CYEST CAPITAL LIMITED | Private company limited by shares | Live |
| HK CYFF DRESS (GROUP) CO., LIMITED | Private company limited by shares | Live |
| CYFG Limited | Private company limited by shares | Dissolved |
| Cyflex Investment Company Limited | Private company limited by shares | Live |
| Cyfoeth Holding Limited | Private company limited by shares | Live |
| STARK CYGG CPA LIMITED | Private company limited by shares | Live |
| CYGLADE LIMITED | Private company limited by shares | Dissolved |
| CYGNA ENTERPRISES LIMITED | Private company limited by shares | Dissolved |
| CYGNE APPAREAL LIMITED | Private company limited by shares | Dissolved |
| CYGNE FAR EAST LIMITED | Private company limited by shares | Dissolved |
| HONGKONG BLACK CYGNE FASHION INTERNATIONAL CO., LIMITED | Private company limited by shares | Dissolved |
| CYGNE GROUP (F.E.) LIMITED | Private company limited by shares | Dissolved |
| CYGNE INTERNATIONAL (HONG KONG) COMPANY LIMITED | Private company limited by shares | Dissolved |
| CYGNE NOIR LIMITED | Private company limited by shares | Live |
| CYGNET LIMITED | Private company limited by shares | Live |
| Cygnett HK Limited | Private company limited by shares | Live |
| CYGNIX LIMITED | Private company limited by shares | Dissolved |
| CYGNUS COMPANY LIMITED | Private company limited by shares | Dissolved |
| Cygnus Asia Limited | Private company limited by shares | Live |
| Black Cygnus Limited | Private company limited by shares | Live |
| Cygnus Equity Brilliance Limited | | Live |
| CYGNUS CO., LIMITED | Private company limited by shares | Live |
| CYGNUS INTERNATIONAL CO., LIMITED | Private company limited by shares | Live |
| CYGNUS CORP. LIMITED | Private company limited by shares | Live |
| CYGNUS ELECTRONICS LIMITED | Private company limited by shares | Live |
| Cygnus Equity Limited | Private company limited by shares | Live |
| Cygnus Finance Limited | Private company limited by shares | Live |
| Gong Fu Cygnus Limited | Private company limited by shares | Live |
| CYGNUS (HONG KONG) COMPANY LIMITED | Private company limited by shares | Live |
| Cygnus Space (Hong Kong) Company Limited | | Live |
| CYGNUS INTERNATIONAL COMPANY LIMITED | Private company limited by shares | Dissolved |
| CYGNUS LIGHT LIMITED | Private company limited by shares | Dissolved |
| Cygnus Management Limited | Private company limited by shares | Live |
| CYGNUS RADIOLOGY COMPANY LIMITED | Private company limited by shares | Dissolved |
| CYGNUS REPRESENTATION LIMITED | Private company limited by shares | Dissolved |
| CYGNUS SATELLITE LIMITED | Private company limited by shares | Dissolved |
| Cygnus IT Solutions HK Limited | Private company limited by shares | Live |
| STAR CYGNUS LIMITED | | Live |
| CYGNUS TRADING CO., LIMITED | Private company limited by shares | Live |
| CYGONKA LIMITED | Private company limited by shares | Dissolved |
| CYGOU LIMITED | | Live |
| Hong Kong CYHD International Co., Limited | Private company limited by shares | Live |
| CYHM COMPANY LIMITED | Private company limited by shares | Dissolved |
| CYHONG LIMITED | | Live |
| CYHX LIMITED | Private company limited by shares | Live |
| C.Y.I. CREATION LIMITED | Private company limited by shares | Dissolved |
| CYIBAI TECHNOLOGY CO., LIMITED | Private company limited by shares | Live |
| C.Y.I.D. Limited | Private company limited by shares | Live |
| CYIDA LIMITED | | Live |
| Cyin Trading Limited | Private company limited by shares | Live |
| CYING ABROAD LIMITED | | Live |
| CYIT CO., LIMITED | Private company limited by shares | Dissolved |
| CYJB Food Limited | | Live |
| CYJB Trading Limited | | Live |
| CYJET INFORMATION TECHNOLOGY (HONG KONG) LIMITED | Private company limited by shares | Live |
| HONG KONG C.Y.K. CLUB LIMITED | Company limited by guarantee | Dissolved |
| C.Y.K. Sourcing Co., Limited | Private company limited by shares | Live |
| CYKAKA TRADE LIMITED | Private company limited by shares | Live |
| CYKing Limited | Private company limited by shares | Live |
| CYKO LIMITED | | Live |
| CYKO COMPUTER LIMITED | Private company limited by shares | Dissolved |
| CYKON TECHNOLOGY LIMITED | Private company limited by shares | Live |
| Cykorp Limited | Private company limited by shares | Live |
| CYKP LIMITED | | Live |
| CYKT Limited | Private company limited by shares | Live |
| CYL2 TECHNOLOGY LIMITED | Private company limited by shares | Live |