Idiopathic interstitial pneumonia is a subset of diffuse interstitial lung diseases. Idiopathic interstitial pneumonia is a heterogenous disorder consisting of several clinicopathological entities with differing histopathological patterns. Due to the fact that all of these entities have different clinical, course, response to therapy, and prognosis, distinquishing these hisologic patterns are mandatory for the accurate determination of prognosis and optimal management in an individual patient. This review mainly concerns the pathologic descriptions of individual patterns of idiopathic interstitial pneumonia and the important features in the differential diagnosis of these patterns.