Pulmonary alveolar proteinosis is a rare disease characterized by the accumulation of lipoproteinosis material within the alveoli. A 36 age male patient applied to our hospital with dyspnea that began 5 months ago. Bilateral diffuse infiltration on postero-anterior chest graphy was seen. Arterial blood gas measurements (ABG) was: pH:7.44, pCO2: 36 mmHg, pO2: 49 mmHg, SaO2: 85%, HCO3: 24 mmol/L. High resolution computed tomography (HRCT) reported as bilateral diffuse ground glass areas and interlobuler septal thickening on this areas. Asido resistant bacillus was negative in sputum at three times and was also negative in post bronchoscopic sputum and bronchoalveoler lavage material. Wedge resection was made by video-assisted thoracoscopic surgery. Histopathology report of biopsy material revealed “Pulmonary alveolar proteinosis (PAP)”. Massive lung lavage under general anesthesia was planned for patient. Clinical improvement was seen in patient beginning from admission and ABG measurements entered the recovery trend in follow-up. Partial pressure of oxygen was increased to 65 mmHg and patient was followed without lung lavage. Control chest radiography and HRCT showed significant radiological improvement. After three months, radiological lesions had completely regressed at control HRCT. As a result, in patients with symptoms and radiologically bilateral diffuse infiltration physicians should consider PAP as a rare disease in the differential diagnosis.