Residual work capacity and inability to work fulltime are important outcomes in disability benefit assessment for workers with mental and behavioural disorders. The aim of this study is to gain insight into the prevalence and associations of socio-demographic and disease-related factors of these outcomes across different mental and behavioural diagnoses groups. A year cohort of anonymized register-data of patients diagnosed with a mental or behavioural disorder who claim a work disability benefit after two years of sick-leave was used (n = 12,325, age 44.5 ± 10.9, 55.5% female). Limitations in mental and physical functioning caused by disease are indicated according to the Functional Ability List (FAL). No residual work capacity was defined as having no possibilities to work, whereas inability to work fulltime was defined as being able to work less than 8h per day. The majority (77.5%) of the applicants were assessed with residual work capacity, of these 58.6% had an ability to work fulltime. Applicants diagnosed with (post-traumatic) stress, mood affective and delusional disorders showed significant higher odds for no residual work capacity and for inability to work fulltime, while other diagnoses groups, like adjustment and anxiety disorders, showed decreased odds for both assessment outcomes. The type of mental and behavioural disorder seems important in the assessment of residual work capacity and inability to work fulltime, as the associations differ significantly between the specific diagnoses groups.