The main topic of this paper is the development of speech of preschool children, Croatian language and its dialects. Throughout the entire study, the aim was to show how the dialects affect the development of children's speech. I’ve made the research that corroborated my hypotheses, which claims that the deviation in speech from the standard Croatian language is assumed for preschool children due to the influence of their local speech and dialects. It is also assumed that there is probably less deviation from a standard Croatian language for children who speak Shtokavian dialect than for the one who speak Chakavian and Kajkavian dialect because of the similarities as well as the differences between those dialects and the standard Croatian language. This survey gives a clearer picture of how the environment, in which children live and the dialects they speak, influence on the development of their speech. Therewithal, it shows how significant are the deviations in the child's speech from their pronunciation of the standard Croatian language.