The purpose of our study is to describe the different levels of speech organization of adults with autism spectrum disorders (ASD) and Mental retardation (MR). Informants in the study were 19 adults aged 29.9 ± 5.8 years (mental age 9–14 years) with autism spectrum disorders (n = 5, 23–41 years, 31 ± 6.5 y) and with mental retardation (n = 14, aged 21–43 year, 29.2 ± 5.8 y). We revealed the specificity of speech features in informants with ASD and MR in complexity of replicas in dialogues, gestures use, adequacy of replicas, phonetic and acoustic characteristics. Attribution of the emotional speech to states “comfort – neutral – discomfort” of the ASD informants is difficult for listeners. The listeners recognized neutral state in speech of ASD and MR informants better than comfort and discomfort states. Our study is the first step towards investigating the problem of the transition from childhood to adulthood for Russian people with atypical development. The findings of our study provide valuable information for health and other professionals working with people with intellectual disability.