Background: Ground-glass opacification/opacity is a non-specific sign with a wide etiology including infection, chronic interstitial disease and acute alveolar disease.  The use of the term ground glass derives from the industrial technique in glassmaking whereby the surface of normal glass is roughened by grinding it. Subtypes of GGO include nodular, mosaic, crazy paving, diffuse, mosaic, centrilobular, halo sign, and reversed halo sign.  A total number of 50 male and female patients were included in the study with age range from 22 to 88 years, and were coming for CT chest study assessment. Aim of the work: The aim of this study is to implement the importance of HRCT with its reconstruction capabilities in the detection of ground glass lesions in diffuse lung diseases and approach for differential diagnosis. Material and methods: This cross sectional study involved 50 patients  with different chest symtomps include dysnpnea, cough or fever. Results: This study involved 50 patients, all above 18 years of age and age range are between (22 to 81) years. According to clinical data, among the studied cases there were 43 (86%) with cough, 8 (16%) with fever and 38 (76%) dyspnea. According to ground glass lesion CT morphology and distribution, among the studied cases there were 33 (66%) ill-defined and 13 (26%) well-defined, there were 15 (30%) with central, 25 (50%) with peripheral and 5 (10%) with both central and peripheral (Cp & P) and there were 14 (28%) with patchy and 20 (40%) with homogenous. Conclusion: HRCT is essential diagnostic tool for diagnosis and characterization of diffuse ground glass opacities. Interstitial lung disease is the most common disease to cause diffuse ground glass opacity followed by inhalation lung disease and pulmonary edema. Multidisciplinary approach with the aid of clinical, laboratory and histopathology were essential to reach the final diagnosis.