A 70-year-old woman with a history of sinobronchial syndrome was admitted to the hospital because of a cough, sputum, and abnormal chest shadow. She was diagnosed with pulmonary mucosa-associated lymphoid tissue lymphoma (p-MALToma) based on results of a pathologic examination and the gene rearrangements in the Ig heavy chain on Southern blot hybridization. Although p-MALToma did not regress with conventional therapy, it was reduced after long-term treatment with clarithromycin (CAM) (200 mg/d). A 57-year-old woman with a history of Sjögren syndrome and lymphocytic interstitial pneumonia had a mass lesion in the left lower lung field. CT image-guided biopsy established a diagnosis of p-MALToma. The p-MALToma regressed with long-term treatment with CAM (200 mg/d), whereas Helicobacter pylori (HP) eradication therapy was not effective in concurrent atrophic gastritis with HP. It is suggested that CAM, a macrolide antibiotic, may be effective in some patients with p-MALToma.