By contrast to adult bipolar disorder(A-BD), there has been considerably controversy about the existence and diagnosis of pediatric bipolar disorder(P-BD).We assessed outcome and psychopathological characteristics of A-BD vs. P-BD. We examined medical records of inpatients with DSM-IV-diagnoses of bipolar disorder. Patients were divided in two groups pediatric versus adult(>18 yrs) onset of bipolar disorder and compared for demographic and clinical data. All admitted patients were evaluated by a rating scale assessing their temperament(TEMPS-A) and DSM-IV diagnosis(MINI). Among seventy-eight patients(pediatric-BD N = 24 vs. Adult-BD N = 54; aged 34.79 ± 11.46 vs. 43.59 ± 12.75), 69% patients had an adult onset of the bipolar disorder. Pediatric-BD patients had a significant longer time of untreated full-blown psychiatric symptoms before first psychiatric contact(DUB) compared to A-BD (Mean pediatric DUB 11.04 ± 12.35 vs. adult DUB 2.23 ± 4.28,p < 0001). At onset P-BD patients had diagnosis of mood disorder in 50% cases compared to A-BD with 77.7% cases(Mood disorder diagnosis N = 12 vs. N = 42, p = .033). Regarding P-BD, most frequently polarity of onset was mixed (N = 12, 52%) versus adult-BD with depressive (N = 28, 58.3%, p = .036). Patients with P-onset showed greater psychosis lifetime compared to A-BD(1.1 vs. 0.6,p = .05). Pediatric-BD had temperament characteristics ranked hyperthimic>cyclothimic>depressive> irritable=anxious, versus adult onset hyperthimic > depressive = irritable > anxious >cyclothimic (p = 03). in our sample patients with early onset tend to maintain over time specific psychopathological characteristics compared to adult onset; this characteristics are often misdiagnosed with a variety of psychiatric diagnosis before the diagnosis of bipolar disorder and specific treatment. No differences were found for outcome measures probabily related to small sample.