Aim. This study aims to investigate self-understanding in young males with high-functioning autism spectrum disorders (ASD) and to determine whether self-understanding is related to social functioning and theory of mind (ToM). In addition, this study aims to examine the characteristics and abilities of young males with high-functioning autism (HFA) and Asperger’s disorder (AD) to determine whether there are significant differences in selfunderstanding and whether self-understanding is related to social functioning and ToM between these two groups. The results have important implications for social skills interventions for young people with ASD. Method. Forty three young males diagnosed with one of the ASD (25 diagnosed with HFA and 18 diagnosed with AD) were compared with 38 TD males. Participants were assessed using the Autism Diagnostic Interview- Revised (ADI-R), the Kaufman Brief Intelligence Test (KBIT), the Vineland Adaptive Behavior Scales (VABS), the Peabody Picture Vocabulary Test- Third Edition (PPVT-III), Damon and Hart’s Self-understanding Interview, and two false-belief ToM tasks. Results. Children with ASD had difficulties recognising and attributing their own mental states and failed to integrate various aspects of the self. Specifically, the ASD group produced fewer self-statements that reflected agency (the awareness and understanding that one is in control of their actions), social aspects of self (such as personality characteristics and group membership) and psychological aspects of self (such as emotions, thoughts and cognitive processes). Instead, children with ASD produced more concrete physical self-statements (such as body characteristics and material possessions). A significant positive relationship was found between selfunderstanding and social functioning for the ASD group. Within the ASD group, the relationship held for the HFA group only. In terms of ToM, children with ASD were less able to correctly answer the second-order false-belief ToM question compared to the TD group. For the ASD group, there was a significant positive correlation between self-understanding and ToM. Within the ASD group, the relationship held for the HFA group only. Conclusions. The results show young males with high-functioning ASD are less aware of their own and others’ mental states perhaps reflecting a general delay in the development of self-understanding and ToM. Furthermore, a more developed self-understanding may translate to improved social functioning and ToM ability for young males with high-functioning ASD. For young males with HFA, self-understanding and ToM may stem from a common underlying cognitive framework. Consequently, treatments aimed at improving self-understanding may simultaneously improve ToM, or vice versa. For individuals with AD there may be a separate cognitive mechanism responsible for self-understanding and another for ToM. Therefore, different interventions may be required; one to improve self-understanding and another to improve the understanding of others’ minds. Overall, these results may assist in the development of practice parameters for social skills training for those with ASD.