Abstract Background. The aim of the present study was to estimate prevalence rates of psychiatric and substance use disorders in male and female prisoners on admission to prison in the north of France and compare the frequency of these disorders to the general population. Methods. This cross-sectional survey on Mental Health in the Prison Population (MHPP), conducted between March 2014 and April 2017, interviewed 653 randomly selected men and women who had recently been committed to the French general population prison system in the Nord and Pas-de-Calais departments. For each subject, the Mini International Neuropsychiatric Interview (MINI), a standardized psychiatric interview, was used to screen for psychiatric and substance use disorders. The prevalence rates were then compared with data from the Mental Health in the General Population (MHGP) survey, a general population survey that used the same assessment methodology as MHPP in the Nord and Pas-de-Calais departments. A control sample was taken from the MHGP survey with a ratio of one case (MHPP) to three controls (MHGP) matching on age and sex. Results. The sample was primarily composed of French men, most of them single with low educational levels at the time of imprisonment. The mean age was 31.7 (standard deviation = 9.9; min = 18; max = 67). Most of the subjects included were first-time prisoners. The prevalence of affective disorders among newly incarcerated individuals was 31.2% with higher rates for major depressive disorder (27.2%). The prevalence of anxiety disorders was 44.4% with higher rates for generalized anxiety disorder (25.2%). The prevalence of psychotic syndromes was 6.9%. The prevalence of substance use disorders was 53.5% and a suicide risk was identified in 31.4% of the prisoners interviewed. Higher prevalence rates were found in the MHPP when compared with the MHGP for all psychiatric and substance use disorders assessed except for dysthymia and current isolated psychotic syndrome. Conclusions. Our study shows very high levels of prevalence for psychiatric and substance use disorders in recently committed French prisoners.