In spontaneous speech the problem of lexical access can occur as the use of incorrect lexemes. The various types of incorrect lexemes can be based on semantic and phonetic similarity, caused by grammatical reasons, mixed idioms or compression report. They can also occur in telling the poems learnt by heart. The incorrect lexemes occurring in these situations have common elements and differences, but the question is to what extent. A series of experiments was carried out with the participation of secondary-school children. Their improved and unimproved incorrect words selected from their spontaneous speech patterns, and their poems learnt by heart were analysed in quantitative and qualitative terms (frequency, types, word orders) both by Praat program and by statistics. The results have confirmed the preliminary assumption and they can offer new input into serving teenagers whose development of typical language mental lexicons may serve for comparison testing of atypical language development.