OBJECTIVE The objectives of this study were: (1) to investigate the effect of age at cochlear implantation (CI) on vocabulary development; (2) to evaluate the age effect at CI surgery on the syntactic development; and (3) to examine the role of gender, age at first diagnosis and maternal education level on spoken language development. METHODS Retrospective study. Thirty children with congenital severe- to -profound sensorineural hearing loss (SNHL) were sampled. They were diagnosed and fitted with hearing aids through six months of age. They were implanted between 8 and 17 months of age. The MacArthur-Bates Communicative Development Inventory (MCDI) was administrated at the age of 36 months. The total productive vocabulary (word number raw score), the mean length of utterance (M3L) and the sentences complexity were analysed. RESULTS The average word number raw score was 566.3 for the children implanted before 12 months of age versus 355 for those implanted later. The M3L was 8.3 for those implanted under 1 year versus 4.2 of those implanted later. The average sentences complexity was 82.3% for those receiving CI before 12 months, while it was 24.4% for those underwent at CI after 12 months. Regression analysis revealed a highly significant and negative linear effect of age at CI surgery on all outcomes. Females had better outcomes. Age at diagnosis was not correlated with the linguistic results. The mother's education level had a positive significant effect on sentences complexity. CONCLUSIONS The CI in pre-school children with SNHL implanted under 1 year has a positive effect on spoken language. Females seem to have better linguistic results. Finally high maternal educational level appears to have some positive effect on language development.