The differential diagnosis of paracardiac lesions includes pericardial cysts (PC), which are benign, developmental lesions. Patients with PC are usually asymptomatic, although chest pain or dyspnea may occur. The diagnosis may be established by chest roentgenogram (radiographic contour and location), fluoroscopy (changes in shape with respiration or positioning the patient), and echography (smooth, cystic contour and characteristic location). We present the diagnostic approach to patients with PC, and a review of the case histories of 12 patients with PC. Two symptomatic patients with PC were treated with surgical excision. Cyst aspiration in two patients yielded clear fluid and was initially considered therapeutic, but was followed by gradual reaccumulation of fluid. Six of ten asymptomatic patients followed for three to ten years did not develop symptoms, nor was there radiographic evidence of progressive PC enlargement. Three of ten died from unrelated causes during the follow-up period. Although symptomatic patients with PC may require surgical excision, asymptomatic patients with PC should be managed conservatively.