Provided is a new drug effective for the prevention or treatment of chronic respiratory diseases such as COPD, interstitial pneumonia and asthma. The therapeutic agent for chronic respiratory diseases is represented by the general formula (1): wherein R1 represents an alkyl group having 4 to 8 carbon atoms, R2 represents a hydrogen atom, an alkylcarbonyl group having 2 to 6 carbon atoms or a carbon atom. A hydroquinone derivative represented by the formula (2-6) is included as an active ingredient.ＣＯＰＤ、間質性肺炎及び喘息といった慢性呼吸器疾患の予防又は治療に有効な新たな薬剤を提供する。 慢性呼吸器疾患治療剤は、一般式（１）【化１】（式中、Ｒ１は炭素数４～８のアルキル基を示し、Ｒ２は水素原子、炭素数２～６のアルキルカルボニル基または炭素数２～６のアルコキシカルボニル基を示す。）で表されるハイドロキノン誘導体を有効成分として含む。
