Children's first-language perception base and their operative strategies of perceptual processes take shape gradually from age one onwards. A large amount of research has been devoted to the analysis of children's speech processing; however, this is the first comprehensive study of the speech perception processes of Hungarian two- and three-year-olds (based on 3360 data of 48 children, using 7 subtests of the GMP diagnostic procedure). The aim of the present research was to characterize the organization of speech decoding processes, the interrelations of speech perception and comprehension as well as the strategies children use. The analysis proved the existence of a strong top-down decoding process which is entirely different from the organization of adults' processes. There was no significant variation across age groups but significant differences have been found depending on the decoding processes themselves. In addition, children's speech perception showed enormous individual differences. The results have important consequences for the practice of speech therapy.