The authors investigated the diagnostic utility of plasma N-terminal pro-B-type natriuretic peptide (NT proBNP) and C-reactive protein (CRP) levels in the differential diagnosis of constrictive pericarditis (CP) and restrictive cardiomyopathy (RC). Twenty-five patients with high clinical suspicion of either CP or RC were enrolled. Mean plasma NT proBNP levels were significantly higher in patients with RC compared to those with CP (2641 +/- 2902 pg/mL vs 628 +/- 678 pg/mL; P=.003). The NT proBNP level that provided the best sensitivity and specificity for the differentiation of CP and RC was 800 pg/mL. Mean CRP levels were higher in patients with CP than with RC (1.41 +/- 1.73 mg/dL vs 0.38 +/- 0.21 mg/dL; P=.03). The CRP level that provided the best sensitivity and specificity for the differentiation of CP and RC was 0.57 mg/dL. Plasma NT proBNP and CRP levels can be useful in the differential diagnosis of RC and CP.