To retrospectively compare the frequencies of computed tomographic (CT) findings in patients with lymphangioleiomyomatosis (LAM) and patients with tuberous sclerosis complex (TSC) and LAM. Institutional review board approval and informed consent were obtained for the HIPAA-compliant study. In 256 patients with LAM (mean age, 44 years) and 67 patients with TSC/LAM (mean age, 40 years), CT scans of the chest, abdomen, and pelvis were reviewed by a single radiologist. The fraction of lung involvement with cysts was estimated from high-spatial-resolution CT scans. Other findings assessed included noncalcified pulmonary nodules, pleural effusion, thoracic duct dilatation, hepatic and renal angiomyolipomas (AMLs), lymphangioleiomyoma (LALM), ascites, nephrectomy, and renal embolization. Confidence intervals and hypothesis tests of differences in frequencies, comparison of age quartiles, RIDIT analysis, analysis of variance, and correlation coefficients were used in the statistical analysis. Patients with LAM had more extensive lung involvement (RIDIT score, 0.36) and higher frequency of LALM (29% vs 9%, P<.001), thoracic duct dilatation (4% vs 0, P=.3), pleural effusion (12% vs 6%, P=.2), or ascites (10% vs 6%, P=.3). Patients with TSC/LAM had higher frequency of noncalcified pulmonary nodules (12% vs 1%, P<.01), hepatic (33% vs 2%, P<.001) and renal (93% vs 32%, P<.001) AMLs, nephrectomy (25% vs 7%, P<.001), or renal artery embolization (9% vs 2%, P<.05). The extent of lung disease is greater in LAM than TSC/LAM. Hepatic and renal AMLs and noncalcified lung nodules are more common in TSC/LAM, while lymphatic involvement-thoracic duct dilatation, chylous pleural effusion, ascites, and LALM-is more common in LAM. Copyright (c) RSNA, 2006.