A 73-year-old woman was admitted to our hospital for investigation of an abnormal shadow in the right upper lung field. Every year she had a medical check up since 1983 and the abnormal shadow was repeatedly pointed out However, she had not undergone a detailed examination. When she had a medical check up in July 2001, the shadow slightly increased compared with the previous chest film. Chest CT showed the mass with a pleural indentation in the right S3a, measuring 4 x 4 cm in size. Despite examinations including bronchoscopy we could not make a definitive diagnosis. After we explained the situation to her, she decided to have an operation. The biopsy during the operation revealed adenocarcinoma and right upper lobectomy with nodal dissection was performed. The ultimate diagnosis was non-mucin-producing papillary adenocarcinoma. This stage IB case was pT2N0M0. We reported this case because it was a rare slow-growing papillary adenocarcinoma that did not produce mucin and had a 19-year clinical history before operation.