| Comex S.A. | Pomeranian |
| Comp S.A. | Masovian |
| COMP Soft Sp. z o.o. | |
| Comp-Win | Greater Poland |
| CompArt International | Masovian |
| Complex Computers Sp. z o.o. | Świętokrzyskie |
| Complex S.C. | West Pomeranian |
| Comprix | Świętokrzyskie |
| CompuTec S.A. | |
| Computer Group Pakt Sp. J | Masovian |
| Computer Plus Kraków S.A. | Lesser Poland |
| Computer Service Expert | Lower Silesian |
| Computersoft | Lower Silesian |
| Computerworld.pl | Masovian |
| Computex | |
| Comsat Sp. z o.o. | Greater Poland |
| Comset S.A. | Lesser Poland |
| ComSoft Radom | |
| Comtegra S.A. | Masovian |
| Comtronic Sp. z o.o. | Lublin |
| ComWeb | Pomeranian |
| Comzit | Masovian |
| Concept Data S.A. | |
| Confitura | |
| Confly | |
| Conlea Sp. z o.o. | Pomeranian |
| Connect Distribution Sp. z o.o. | Masovian |
| Connecta | Lower Silesian |
| ConnectPoint Sp. z o.o. | |
| Conor Interactive | Masovian |
| Consdata S.A. | |
| Consonance Sp. z o.o. | Lesser Poland |
| Contact Center Sp. z o.o. | Masovian |
| Contec IT Sp. z o.o. | Masovian |
| Contec Sp. z o.o. | |
| Context Sp. z o.o. | |
| Control System FMN Sp. z o.o. | Masovian |
| Controlling Systems Sp. z o.o. | Lower Silesian |
| Convel Sp. J. | Masovian |
| Copernicus Center | |
| Copix Sp. z o.o. | Masovian |
| Copoint Sp. z o.o. | |
| CorCode | |
| CorCode Sp. z o.o. | |
| CorNet | Pomeranian |
| Correscopy | |
| Corsario.pl | Lower Silesian |
| Cortland | Silesian |
| CosmoEye | Lublin |
| CoverNET | Subcarpathian |