Prevalence rates of depression and anxiety among migrants (i.e. refugees, labor migrants) vary among studies and it's been found that prevalence rates of depression and anxiety may be linked to financial strain in the country of immigration. Our aim is to review studies on prevalence rates of depression and/or anxiety (acknowledging that Post-traumatic Stress Disorder (PTSD) is within that class of disorders), and to evaluate associations between the Gross National Product (GNP) of the immigration country as a moderating factor for depression, anxiety and PTSD among migrants. We carried out a systematic literature review in the databases MEDLINE and EMBASE for population based studies published from 1990 to 2007 reporting prevalence rates of depression and/or anxiety and or PTSD according to DSM- or ICD- criteria in adults, and a calculation of combined estimates for proportions using the DerSimonian-Laird estimation. A total of 348 records were retrieved with 37 publications on 35 populations meeting our inclusion criteria. 35 studies were included in the final evaluation. Our meta-analysis shows that the combined prevalence rates for depression were 20 percent among labor migrants vs. 44 percent among refugees; for anxiety the combined estimates were 21 percent among labor migrants vs. 40 percent among (n=24,051) refugees. Higher GNP in the country of immigration was related to lower symptom prevalence of depression and/or anxiety in labor migrants but not in refugees. We conclude that depression and/or anxiety in labor migrants and refugees require separate consideration, and that better economic conditions in the host country reflected by a higher GNP appear to be related to better mental health in labor migrants but not in refugees.