The preoperative assessment before pulmonary resection is both important and difficult. Pulmonary function testing is imperative to assess pulmonary reserve. If the FEV1 is less than 2 L, differential perfusion lung scans are used for a more accurate assessment. Exercise testing may also be used as an adjunct for high-risk patients or procedures. Although a predicted postoperative FEV1 of 800 mL is a widely accepted minimum for resection, it has not been scientifically validated. Lesser procedures (segmentectomy and wedge resection) may be performed with acceptable mortality in patients who were previously not considered surgical candidates.