Positron emission tomography/computed tomography (PET/CT), as any other imaging modality, is acceptable for routine clinical and research applications only if technical pitfalls can be avoided. Artefacts from incorrect or sub-optimal acquisition procedures should be recognized and, if possible, corrected retrospectively and the resulting image information interpreted correctly, which entails an appreciation of variants of the represented image information. This publication provides guidance on the physics and technical aspects behind PET and PET/CT image distortions. Cases are presented to provide nuclear medicine and radiology professionals with an assortment of examples of possible image distortions and errors in order to support correct image interpretation. Nearly 70 typical PET and PET/CT cases, comprising image sets and case description, have been collected in this volume, all catalogued and augmented with explanations as to the causes of, and solutions to, each individual image problem. The atlas will prove useful to physicists, physicians, technologists, and service engineers in the clinical field.