We encountered three patients with synchronous double cancers in the lung and stomach. Although the gastric cancers were resected curatively in all three patients, the lung cancers were resected palliatively because they were too advanced for curative resection. In the Japanese literature we found 25 operated cases of synchronous double cancers and 24 operated cases of metachronous double cancers in the lung and stomach. Early diagnosis and curative resection of both cancers improve the survival rate of these primary double cancers.