Background: Considerable controversy exists regarding clinical presentation, diagnosis, and comorbidities especially with Attention Deficit Hyperactivity Disorder (ADHD), in paediatric Bipolar Disorder (BPD). Aims and objectives: To describe phenomenology and comorbidities of paediatric BPD. Method: 78 Subjects (6-16 years) attending child and adolescent psychiatry services of C.S.M.M.U. Lucknow, who fulfilled DSM-IV-TR 2000 criteria for BPD were assessed using K-SADS-PL, child mania rating scale (CMRS),child depression rating scale (CDRS), Attention Deficit Hyperactivity Disorder rating scale (ADHD-RS) and Clinical Global Assessment Scale (C-GAS). Results: All the subjects were diagnosed as BPD-I. There mean chronological age was 13.4 plus or minus 2.1 years. The mean age at onset of BPD was 12.2 plus or minus 2.3 years. The most common symptoms found in manic subjects were increased goal directed activities (100%), distractibility (100%), elation (98.7%), grandiosity (90.5%), physical restlessness (82.4%), poor judgment (82.4%) and decreased need for sleep (81.1%). 19 (24.3%) cases of BPD had other current comorbid disorders. The common comorbidities were Mental Retardation (10.26%), ADHD (10.26%), oppositional defiant disorder (6.41%), and substance abuse (3.85%). Conclusions: In children and adolescents elation/grandiosity was more common presentation than Irritability. Comorbidities were seen in 24.3% children in paediatric BPD. Differentiation of comorbid disruptive behaviour disorders especially ADHD from BPD is possible with respect to age of onset, quality of the disturbed mood, and the course of each disorder.