Attention-deficit hyperactivity and bipolar disorders share symptoms: attention deficit, hyperactivity, impulsiveness and irritability. In fact, most of the diagnostic criteria for hyperactivity are present in mania. The Conners rating scale, universally used by teachers, does not allow the clinician to discriminate between both entities, leading to misdiagnosis, specially when the doctor bases his/her diagnosis in the scale and not in a detail interview. This article attempts to guide in diagnostic criteria that allows the clinician to differentiate both entities, based on the most relevant and orientating contemporary literature