To determine the clinical picture of bipolar affective disorders (BD) in children and adolescents hospitalized at the Clinical Ward of Developmental Age Psychiatry and Psychotherapy (DAPP) in Sosnowiec, Poland. Documentation analysis of 288 BD patients below 18 years of age. Detailed clinical and demographic data were collected and symptoms present during hospitalization were assessed. The mean age of illness onset was 13.6 ± 1.7 years. A total of 86.5% of the studied individuals received a first diagnosis different from BD/mania, and the average time until the proper diagnosis was 16.9 months. In 45.5% the first episode was depression with varied severity, in 29.2% a mixed episode and in 25.3% mania/hypomania. In 48.6% comorbid disorders were present. The most frequent reason for hospitalization was a mixed episode (47.6%). Among the symptoms, irritability was observed in over 80% of patients with mania or mixed episodes, but also in 60% of patients with depression. Suicidal thoughts were experienced by almost all the depression patients, 84.7% in the mixed episode and also 52.6% in mania/hypomania episode. Anxiety was mostly present in depression (40.7%) and mixed episode (22.6%), while moodcongruent delusions in depression and mania (around 20% of cases). Aggressive behaviours were manifested in around half of patients with mania and a mixed episode. In the studied population of children and adolescents, BD usually started with a depression episode accompanied by a high rate of comorbid disorders and in most cases there was an original misdiagnosis. Study results also point to a significant frequency of some pathological symptoms in this population.