The article presents the results of research on the implementation of sounds in the speech of Polishspeaking children with specific language impairment (SLI). In Polish speech-therapy literature, little space is devoted to the analysis of the phonetic and phonological problems of these children, hence an attempt was made to elaborate on this issue. Eight children with a clinically confirmed diagnosis of SLI participated in the study. The diagnosis was made based on the diagnostic inclusion and exclusion criteria in the ICD-10. The children were tested with the 100-word articulation test. The children’s statements were recorded with a voice recorder and then analyzed using the listening method in the EXMARaLDA software. All the sounds of the Polish language were subject to linguistic analysis. Based on the research results, many phonetic and phonological processes distorting the sound form of sounds have been distinguished. Fields of substitution for all sounds were developed; universal substitutes were distinguished; and the so-called phonetic knots and atypical phonological errors were identified. An attempt was made to explain the causes of phonetic and phonological difficulties in the speech of the examined children.