Nephrolithiasis (NL) and primary hyperparathyroidism (HPTH) are metabolic complications of Paget's Disease of Bone (PDB), but recent data regarding their prevalence in PDB patients are lacking.Study 1: To compare the prevalence of primary HPTH and NL in 708 PDB patients and in 1803 controls. Study 2: To evaluate the prevalence of NL-metabolic risk factors in 97 PDB patients with NL, 219 PDB patients without NL, 364 NL patients without PDB and 219 controls, all of them without HPTH.Cross-sectional multicentric study.Italian referral Centers for metabolic bone disorders.PDB patients from the AIP (Associazione Italiana malati di osteodistrofia di Paget) registry. Participants to the Olivetti Heart and the Siena Osteoporosis Studies.HPTH; NL; NL-metabolic risk factors.PDB patients showed higher prevalence of primary HPTH and NL compared to controls (p&0.01). The NL recurrence occurs more frequently in patients with polyostotic PDB. About half of PDB patients without NL showed one or more NL-related metabolic risk factors. The hyperoxaluria (HyperOx) prevalence was higher in PDB patients with NL compared to NL patients without PDB and in PDB patients without NL compared to controls (p=0.01). PDB patients with HyperOx showed a longer lapse of time from the last aminobisphosphonate treatment.NL and HPTH are frequent metabolic complication of PDB. The NL occurrence should be evaluated in PDB patients, particularly in those with polyostotic disease and/or after aminobisphosphonate treatment, in order to apply an adequate prevention strategy.