Child's language develops very rapidly in the period of toddlerhood, both in terms of qualitative and quantitative developmental changes. Toddler's gender and parental education are two of the most important factors of his/her language development. As the period of toddlerhood represents the critical period for the development of language and early as well as later literacy, the researchers frequently try to establish which instruments and social contexts could provide the most valid and reliable measures of toddler's language competence. The paper describes two Slovenian studies, which included toddlers, aged from 16 to 30 months, attending preschool institutions. To assess toddler's language competence, we used the Inventory of communicatice competence for children aged 16 to 30 months: words and sentences (Marjanovič Umek, Fekonja, Kranjc & Bajc 2008 a). In the first study which included 953 toddlers, we estimated the effect of toddler's genderand their parents' education on toddlers' language competence; in the second study, which included 140 toddlers, we analyzed the agreement between the reports of toddlers' language competence, provided by their parents and preschool teachers. The results of the first study suggests that the toddler's gender and parental education represents important factors of toddler's language development. Parents assessed the language competence of girls with higher rates than the language competence of boys, while the parents with higher education reported of higher language competence of their toddlers than parents with lower education. The findings of the second study shows that, although the parents and preschool teachers listen to and speak with toddlers in different contexts, they assess their language competence with relatively similar rates. However, the toddler's gender and parental education did not have the same effect on the reports given by parents and preschool teachers.