The concepts of the modern computer-aided diagnosis (CAD), the methods of pulmonary nodules detection and facts derived from the available literature on the pulmonary nodule differential CAD topic are compiled in one source and described in some details. Several issues of the lung cancer epidemiology and an early diagnosis are discussed. The analysis of the performed research shows an evidence that various CAD systems can be successfully applied for chest radiographs, computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET). These modalities can serve as a useful tool for a practicing medical professional facing the burden of a routine diagnostic job.