We evaluated diagnosis and treatment of four cases of meningeal carcinomatosis associated with primary lung cancer: case 1; small cell carcinoma (64 years old), case 2; small cell carcinoma (50 years old), case 3; adenocarcinoma (53 years old), and case 4; adenocarcinoma (55 years old). Determination of tumor markers in cerebrospinal fluid (CSF) together with the MRI findings that Gd-DTPA-enhanced T1-weighted image showing high intensity signal along the spinal cord was clinically useful in the diagnosis of meningeal carcinomatosis. Two of four patients received intrathecal chemotherapy and/or CSF drainage through Ommaya-Reservoir, resulting in dramatic improvement of various symptoms such as motor weakness and vesicorectal disorder. Intrathecal chemotherapy and placement of an Ommaya-Reservoir for CSF drainage should be considered to provide better Quality of Life (QOL) when patient can tolerate it.