This study investigated the development of Polish #sC clusters (word-initial /s/+ consonant clusters) in typically-developing children and in children with phonological disorders. Data from 49 Polish-speaking children were analysed in terms of correct and incorrect productions, possible groupings according to the sonority index and the continuancy of the second member of the cluster. While a great deal of variability occurred both within and across children, a number of general findings are indicative of the roles of language-specific vs language-universal factors. For correctness of productions, sonority distance between the members of the cluster did not affect accuracy. In contrast, for the reduction of the targets, the continuancy of the second member played a significant role. Results give support to language-specific patterns in correctness of realizations but follow the universal patterns in reduction.