This book aims to help the reader confused by a multiplicity of diseases responsible for similar symptoms in different patients. Consequently, the chapters are noticeably sign-oriented rather than disease-oriented, each dealing with one of the four cardinal modalities of HRCT presentation, namely the reticular, nodular, alveolar and cystic patterns. Each chapter is introduced by a list of diseases, immediately followed by a detailed description of each disease. All the chapters are thoroughly illustrated with high-quality, enlarged images which, like a counterpoint, provide the rhythm to the written text. When dealing with the diseases within each pattern, only the pertinent manifestations are taken into account. This is a feature unique to this book, which sees the same disease being introduced more than once. This distinction is not artificial, since different phases in the progression of a process not only have different clinical features, but also dissimilar pathological findings, and therefore different radiological aspects. Often, clinical presentation, history and HRCT are sufficient for making a diagnosis and defining disease management; in other cases, further investigation is required to obtain a more confident diagnosis or to determine the activity of the disease more precisely. Consequently, the contributions of other techniques involved in diagnostic refinement are also highlighted (bronchoalveolar lavage, bronchoscopic or thoracovideoscopic biopsy, open chest surgery).