Pulmonary function tests (PFTs) provide important quantitative information about lung function and can be used to elucidate pathologic conditions responsible for respiratory symptoms, assess the severity and course of disease, and evaluate the patient for suitability and timing for lung transplantation. They are typically used in tandem with chest imaging, along with other ancillary data, to arrive at a specific diagnosis. PFTs may provide the radiologist with clues to the diagnosis and grading of a wide variety of pulmonary diseases. In this review, the authors discuss the clinical use of PFTs, their major components, and important measurements and graphical representations that are essential for understanding and interpreting the results. The key components of PFT panels-static lung volumes, dynamic lung function (spirometry), and diffusion capacity-are explained. The authors present a general algorithmic approach for problem solving, with recognition of common patterns of results (obstructive, restrictive, mixed, nonspecific, and normal). Pulmonary diseases from each of the major patterns and chest imaging are illustrated, and correlations between particular PFT results and disease severity and morphology at imaging are examined. Common pitfalls encountered during interpretation are also highlighted. A basic understanding of the mechanics of PFTs, characteristic patterns in important diseases, and correlation between lung function and imaging findings may assist the radiologist in diagnosis and follow-up of key pulmonary diseases and strengthen the radiologist's role as part of a multidisciplinary diagnostic team. Online supplemental material is available for this article. ©RSNA, 2017.