Cardiovascular risk (CVR) has been observed to be higher in patients with severe mental illness (SMI) than in the general population. However, some studies suggest that CVR is not equally increased in different subgroups of SMI. The purposes of this review are to summarise CVR scores of SMI patients and to determine the differences in CVR between patients with different SMIs and between SMI patients and the control-population. Methods MEDLINE (via PubMed) was searched for literature published through August 28, 2014, followed by a snowball search in the Web of Science. Observational and experimental studies that reported CVR assessments in SMI patients using validated tools were included. The risk of bias was reported using STROBE and CONSORT criteria. Pooled continuous data were expressed as standardized mean differences (SMD) with 95 % confidence intervals (CI). Two reviewers independently selected studies, extracted data and assessed methodological quality. Results A total of 3,608 articles were identified, of which 67 full text papers were assessed for eligibility and 35 were finally included in our review, in which 12,179 psychiatric patients and 225,951 comparative patients had been assessed. The most frequent diagnoses were schizophrenia and related diagnoses (45.7 %), depressive disorders (14.7 %), SMI (11.4 %) and bipolar disorders (8.6 %). The most frequent CVR assessment tool used was the Framingham risk score. Subgroups analysis showed a higher CVR in schizophrenia than in depressive disorder or in studies that included patients with multiple psychiatric diagnoses (SMD: 0.63, 0.03, and 0.02, respectively). Six studies were included in the meta-analysis. Total overall CVR did not differ between SMI patients and controls (SMD: 0.35 [95 % CI:−0.02 to 0.71], p = 0.06); high heterogeneity was observed (I 2 = 93 %; p < 0.001). Conclusions The summary of results from studies that assessed CVR using validated tools in SMI patients did not find sufficient data (except for limited evidence associated with schizophrenia) to permit any clear conclusions about increased CVR in this group of patients compared to the general population