PURPOSE: The aim of this study was to evaluate the clinical usefulness of [(11)C]choline positron emission tomography (PET)/CT in comparison with bone scintigraphy (BS) in detecting bone metastases (BM) of patients with biochemical progression after radical treatment for prostate cancer (PCa). METHODS: Seventy-eight consecutive patients with biochemical progression of PCa (mean prostate-specific antigen 21.1 ng/ml, range 0.2-500.0 ng/ml) referred for both [(11)C]choline PET/CT and BS for restaging purposes were retrospectively analysed. The diagnostic accuracy of [(11)C]choline PET/CT and BS was assessed by using morphological imaging and/or follow-up as standards of reference. As equivocal findings were found, the accuracy analysis was performed twice, once including them as positive and once as negative. A separate analysis was also performed in hormone-resistant patients and data compared with those of patients who did not receive anti-androgenic treatment. RESULTS: Equivocal findings occurred in 1 of 78 (1%) cases in [(11)C]choline PET/CT and in 21 of 78 (27%) cases in BS. Depending on their attribution as either positive or negative, the ranges of sensitivity, specificity, positive predictive value, negative predictive value and accuracy for [(11)C]choline PET/CT were 89-89%, 98-100%, 96-100%, 94-96% and 95-96%, respectively. For BS they were 100-70%, 75-100%, 68--100%, 100-86% and 83-90%, respectively. Concordant findings between [(11)C]choline PET/CT and BS occurred in 55 of 78 (71%) cases. The accuracy of [(11)C]choline PET/CT did not significantly (p = 0.30) differ between hormone-resistant patients (97%) and those who did not receive anti-androgenic treatment (95%). CONCLUSION: In clinical practice, [(11)C]choline PET/CT may not replace BS because of its lower sensitivity. However, for its high specificity, [(11)C]choline PET/CT positive findings may accurately predict the presence of BM. Equivocal findings are more frequent in BS than [(11)C]choline PET/CT.