Objective To investigate the value of 18F-fluorodeoxyglucose (FDG) PET/CT in the diagnosis of different pathological types of primary osseous malignant tumors (POMT) in patients over 40 years old. Methods Fifty-two patients (30 males, 22 females, median age: 60(41-81)years) with POMT who underwent 18F-FDG PET/CT and were pathologically confirmed from January 2013 to May 2018 in Cancer Hospital of Tianjin Medical University were reviewed. The region of interest was drawn and the standardized uptake value (SUV) was automatically measured. The SUV in different pathological types of POMT was compared using one-way analysis of variance or two-sample t test. Results The 52 POMT included 22 sarcomas, 16 isolated myelomas (IM), and 14 primary bone lymphomas (PBL). The SUV in PBL was significantly higher that than in sarcomas and IM with the maximum SUV (SUVmax) of 21.6±12.4, 13.5±7.7 and 9.0±6.4 respectively(F=7.56, P<0.01), and the mean SUV (SUVmean) of 12.9±7.8, 7.5±4.5, and 5.6±4.4, respectively(F=6.92, P<0.01). In the sarcoma group, the SUV of undifferentiated sarcomas was significantly higher than that of other well-differentiated sarcomas (SUVmax: 21.1±5.4 vs 11.3±6.9, SUVmean: 11.8±3.3 vs 6.3±4.1; t=-2.92, -2.71, both P<0.01). The growth pattern of sarcomas and IM was different on CT images. Conclusions The FDG uptake of PBL is higher than that of other pathological types. CT features are helpful for the differential diagnosis of POMT in 18F-FDG PET/CT. Key words: Bone neoplasms; Middle aged; Aged; Positron-emission tomography; Tomography, X-ray computed; Deoxyglucose