Pneumonia due to Rothia dentocariosa is extremely rare: only 1 case of pneumonia due to this pathogen has been reported in an immunocompromised patient with acute myelocytic leukemia. In this report, 2 new cases of Rothia dentocariosa pneumonia are described in 2 patients with lung cancer. This opportunistic pulmonary agent, belonging to the oro-pharyngeal flora, is also known to cause endocarditis in patients with underlying cardiac pathology.