The selection of candidates for lung transplantation requires an appreciation of the natural history of lung disease to determine when the disease has entered an advanced and imminently life-threatening stage. It also requires an understanding of the impact of preexisting medical comorbidities on transplant outcomes. Finally, selection is influenced by the particular metric by which outcomes are judged to be successful (e.g., maximizing short-term net survival benefit versus maximizing post-transplant longevity). This article will discuss general and disease-specific criteria used to select patients for lung transplantation and determine the appropriate timing of listing. It will highlight current guidelines put forth by the International Society of Heart and Lung Transplantation and will explore the published data upon which these guidelines are based.