The term hamartoma was first used by Albrecht to describe what he considered to be localized errors of development involving one or more tissue native to the organ of origin. The definition was meant to encompass not only abnormal local growth rate, but also the spatial arrangement, relative proportions and degree of the component tissue. But lately the major conclusions are that this group of lesion is neoplastic than developmental in origin. The Importance of pulmonary hamartoma is that they are relatively common among the benign tumor of the lung, but they usually present as asymptomatic coin lesion on chest x-ray film and were find out In routine check up and frequently mimic clinically the more common lung tumor such as cancer. Recently, we have experienced three cases of pulmonary hamartoma which were all discovered during routine chest film check up for certificate of health and evaluation of other disease. All of these were surgically resected with good result. Among the operations, one of these was mass enucleation and the others were lobectomy of lung involved by the mass.[KTCS 1982;2:155-161]