In obesity, especially if visceral, and in rheumatic diseases, the production of pro-inflammatory cytokines contributes to an increased cardiovascular risk. Moreover, classic cardiovascular risk factors are more common in these patients. We intended to assess the influence of body mass index (BMI), abdominal circumference (AC) and metabolic syndrome (MS) on disease activity and quality of life in Rheumatoid Arthritis (RA) and Psoriatic Arthritis patients and to compare the results between the RA and PsA patients. We performed a cross-sectional study, including 150 patients with RA and 75 patients with PsA. PsA patients had significantly higher BMI, AC and total of comorbidities than RA patients . Independently the underlying pathology (RA or PsA), the number of comorbidities was correlated positively with DAS28, HAQ , CRP and ESR. In RA group, overweight/obesity (BMI≥25kg/m2) were associated with at least one painful joint and the risk of having at least one swollen joint was 3.4 times higher in patients with increased AC. There was an association between the BMI and AC and the CRP value. Patients with BMI≥25 kg/m2 and increased AC had significantly higher DAS28 scores. MS was associated with significantly higher ESR. There was a positive correlation of both BMI and AC with HAQ and also MS was associated with highest HAQ values. In PsA group, patients with BMI≥25kg/m2 had equally more painful joints and higher CRP values. Patients with MS had higher CRP values, more joint pain and higher disease activity according to DAS28. None of the patients with normal BMI had swollen joints, however 20.4% of overweight patients had at least one swollen joint. The number of comorbidities showed to influence inflammatory parameters, disease activity and quality of life. We found that BMI, AC and MS are associated with disease activity, which may be improved by weight reduction and comorbidities control.