| SEO Factory | |
| SEO Marketing Agency | |
| SEO Monitor | Bucharest |
| SEO365.ro | |
| SEOClub | |
| SeoCluj.ro | |
| SEOlympic | |
| SEOmonitor | Bucharest |
| Seopikweb.ro | Bucharest |
| Serra Software International | |
| Servel S.R.L. | Bucharest |
| Server Admin | Bucharest |
| serveresecond-hand.ro | Bucharest |
| Service Laptop Express | Bucharest |
| Servicii SEO Bucuresti | |
| Serviciul de Telecomunicații Speciale | |
| Sether | Bucharest |
| Share IT Smart | |
| Shop4PC | Bucharest |
| ShopGSM | Bucharest |
| ShortPixel | |
| Sian Image Media | Constanța |
| Siel Invest S.R.L. | Bucharest |
| Sigad | |
| SignsFactory | |
| Sigtree | |
| SII Romania | |
| Silkweb | Maramureș |
| Sim Soft Distribution S.R.L. | Cluj |
| Simion Stoilow Institute of Mathematics of the Romanian Academy | Bucharest |
| SimpliQ S.R.L. | Cluj |
| Sintec S.R.L. | Maramureș |
| SIS | Bucharest |
| SisleyStudio | Sibiu |
| Sistec | |
| Site Expert | Bucharest |
| Siteclick | |
| SiteuriWeb | Bucharest |
| SiteXDesign | Iași |
| Sitline Technology | |
| SIVECO Romania | Bucharest |
| Sky Group | Timiș |
| Sky Soft S.R.L. | |
| Smarsoft Electronic S.R.L. | |
| Smart Computers Iasi | Iași |
| Smart Event Marketing | |
| Smart Id Dynamics S.A. | Bucharest |
| Smart Media Interactive S.R.L. | Argeș |
| Smart Protection | |
| Smart Recruit | |