The present invention provides a prophylactic or therapeutic agent for dementia, Alzheimer's disease, attention-deficit hyperactivity disorder, schizophrenia, eating disorders, obesity, diabetes, hyperlipidemia, sleep disorders, narcolepsy, sleep apnea syndrome, circadian rhythm disorder, depression, allergic rhinitis or other diseases. A dihydroquinolinone derivative represented by formula (1) or a pharmaceutically acceptable salt thereof: {wherein Q represents the following formula (A) or (B)}
