Primary lobule, acinus and secondary lobule are the three basic elements of lung tissue. In order to visualize these structures slices of fixed lungs are documented radiologically by plain films, angio-, and bronchograms. Characteristic pathologic alterations of these elements are edema and inflammation. Both lesions present with atypical radiological pattern. In pneumonia it is shown, that differentiation of air conducting structures of the bronchial tree and structures which are involved in gas exchange appears most valuable for interpretation of confluent densities. According to our experience based upon examination of 143 lung specimens separation into lobules is pathophysiological more important than the organisation into the next smaller unit--the acini: patterns of acinar radiodensities are extremely rare and might sometimes be imitated by peribronchial infiltrations.