Atypical adenomatous hyperplasia (AAH) has been considered to be a precursor lesion of bronchioloalveolar carcinoma (BAC) and pulmonary adenocarcinoma. It usually coexists with BAC and/or an adenocarcinoma. Chest computed tomography reveals multiple well-defined nodules with ground-glass opacity. Usually, AAH does not exceed 10 mm in size. AAH with extensive involvement on one side of the lung field or one that is larger than 2 cm has not been previously reported. We herein report a case of a 71-year-old nonsmoking female with lung AAH of larger than 2 cm.