Objective: The aim of the current study was to investigate the differences in baseline characteristics and three-year outcomes between two diagnostic categories with presentation of first-episode psychosis: bipolar affective disorder (mania with psychotic features) and schizophrenia. The comparison was based on pre-treatment characteristics, clinical presentation, symptomatic and functional outcomes, and engagement in risk behaviours. Methods:461 schizophrenic patients and 54 bipolar affective disorder (BAD) patients between the ages of 15 to 25 years from a local first-episode psychosis treatment program within the years2001 to 2003 were studied. Researchers collected detailed data on baseline and three-year follow up variables from systematic medical file review for statistical analyses. Results: At service entry, compared to schizophrenic patients, bipolar affective disorder(BAD)patients exhibited more prominent positive symptoms (p = 0.01), were younger at first presentation and had a higher unemployment rate (p < 0.01), were more likely to have acute onset of psychosis, shorter duration of untreated psychosis (DUP), a higher rate of hospital admission within first month after initial contact, and lower pre-treatment functioning (Social and Occupational Functioning Assessment Scale (SOFAS), p < 0.001). There was no significant difference in gender, education level, age of onset and pre-treatment risk taking behaviours. After applying univariate analysis of variance (ANCOVA)by controlling baseline variables that showed significant differences, the three year follow up reveals that schizophrenic patients displayed fewer numbers of hospitalization (p <0.01)with no difference in the total length (days) of hospitalization, more prominent positive symptoms(p < 0.01), poorer functioning at year 3 (p <0.05), and consistently significant lower employment rate at 12 month (p < 0.001), 24 month (p < 0.001) and 36 month (p < 0.01). Finally, more schizophrenic patients received social benefits (p < 0.05). Conclusion: The outstanding baseline poorer functioning level of bipolar affective disorder patients have progressively made a modest improvement in functional outcomes at the end of three-year follow up. BAD patients also displayed a marked improvement with fewer positive symptoms in the follow up. The results suggest a differentiation in symptomatology and the course of illness between bipolar affective disorder and schizophrenia with first-episode psychosis. In coherence with other scholastic literature, duration of untreated psychosis (DUP) associates with remission(Crumlish et al., 2009;Chang et al., 2012a), positive symptoms(Barnes et.al., 2008; Chang et.al., 2012b; Clarke et al., 2006; Crumlish et.al., 2009;), and functional outcomes(Barnes et al., 2008; Chang et al., 2012b; Clarke et.al., 2006; Crumlish et.al, 2009; Fusar-Poli et al., 2009). Moreover, further exploration about the diagnostic-specific therapeutic window for early intervention, symptoms management, and rehabilitation strategies in occupational training are in demand. / published_or_final_version / Psychological Medicine / Master / Master of Psychological Medicine