Few studies have investigated the association between spinocerebellar ataxia type 3 (SCA3) and psychiatric disorders, using mainly screening scales to assess signs and symptoms of depression and anxiety. With these limitations in mind, we assessed the prevalence of DSM-IV Axis I psychiatric disorders in SCA3 patients and their possible associations with the length of CAG repeats and socio-demographic characteristics, highlighting potential risk factors. DNA samples were collected from 59 adults diagnosed with SCA3 for the quantification of CAG repeats. Next, the patients were assessed in respect to the presence of psychiatric disorders with the Structured Clinical Interview for DSM-IV. Approximately half of the sample had at least one psychiatric disorder (mood disorders 45.2 %), mainly dysthymia and current depression. There were no statistically significant differences in the length of CAG repeats between subjects with and without psychiatric disorders. The perception that SCA3 has a negative impact on life and the subjective assessment of current health status as poor emerged as risk factors for the occurrence of psychiatric disorders in the sample. There is a higher prevalence of psychiatric disorders in SCA3 patients compared to the general population. The lack of association between CAG repeats and occurrence of psychiatric disorders lends support to the hypothesis that psychiatric disorders in this group are associated with adaptive emotional responses to becoming ill.