PROBLEM TO BE SOLVED: To provide a novel prophylactic or therapeutic agent of attention deficit/hyperactivity disorder.SOLUTION: Disclosed is a therapeutic agent which contains the following formula or a salt thereof, particularly (S)-N-[2-(1,6,7,8-tetrahydro 2H-indeno [5,4-b] furan-8-yl) ethyl] propionamide (generic name: ramelteon), or contains ramelteon in combination with at least one agent selected from the other prophylactic or therapeutic agent of attention deficit/hyperactivity disorder.【課題】新規な注意欠陥・多動性障害の予防または治療剤の提供。【解決手段】下記式で表される化合物又はその塩、特に（Ｓ）－Ｎ－［２－（１，６，７，８－テトラヒドロ－２Ｈ－インデノ［５，４－ｂ］フラン－８－イル）エチル］プロピオンアミド（一般名：ラメルテオン）を含有するか、又はラメルテオンと他の注意欠陥・多動性障害の予防又は治療剤から選択される１種以上の薬剤とを組み合わせて含有する治療剤。【選択図】なし
