Congenital cystic adenomatoid malformation of the lung (CCAM) is characterized by an adenomatoid proliferation of bronchiole-like structures and cysts formation. The condition is most commonly found in newborns and children and it may be associated with other malformations; rarely, the presentation is delayed until adulthood. This paper presents a case of CCAM in a 62-year-old male, who presented with recurrent bacterial pneumonias and breathlessness one exertion. The chest X-rays and CT scan revealed a patchy opacity in the right lower pulmonary zone. Bronchoscopic examination was normal. At surgery, a mass involving the right lower and middle lobes, and enlargement of hilar lymph nodes were found. A bilobectomy was performed without complications. Examination of the gross specimen showed a lesion characterised by multiple small cysts, all less than 1 cm in diameter; they were lined predominately by columnar epithelium, occasionally by ciliated epithelium. Rare cysts were lined by foreign body giant cells. Elastic fibers and smooth muscle were present within the cysts wall. Peripherally, there were normal alveoli and bronchioli mixed with cysts, and plasmalymphocytic infiltrates. The final diagnosis was Stocker's Type II CCAM of the lung. CCAM of the lung is a rare development lesion of the lung and it has no sexual predilection. It is usually unilateral and sublobar or lobar in size, but occasionally it can be multilobar. Typical histologic feature of CCAM are adenomatoid proliferation of bronchiole-like structures and macro- or microcysts lined by columnar or cuboidal epithelium and absence of cartilage and bronchial glands. Inflammatory changes are not found in infants, but may be present in adult patients. Based on the size of the cysts, CCAM may be classified into three different types: type I characterised by multiple cysts, over than 1 cm in diameter; type II with smaller cysts, less than 1 cm in diameter; type III that shows solid lesions composed of bronchiole-like structures. Type II is commonly found in childhood, but is occasionally seen in adult patients, as that one in our report. The insult probably occurs between 4th and 7th week of fetal life. The etiologic agent is unknown. The histologic diagnosis of CCAM is difficult in adult patient, perhaps because of supervening infections that sometimes distort the underlying diagnostic pathologic appearances and make them difficult to recognise, as happened in our case. From the clinical point of view, most of the lesions cause severe respiratory failure; in adult individuals the diagnosis is difficult, since there are very few relevant symptoms and signs. The patients can present with fever, recurrent infections, breathlessness and haemoptysis. The chest X-rays abnormalities are not specific and include homogeneous or multicystic opacities. Similarly, other diagnostic methods add no further useful informations. Surgical treatment is necessary also in adult patients, because of the risk of recurrent pulmonary infections and malignancies associated with CCAM. Lobectomy is the treatment of choice, but sometimes a larger resection is required, when the lesion involves more than one lobe.