OBJECTIVES: Immuno-mediated inflammatory diseases (IMIDs) may coexist within the same patient. Anti-TNFs have been shown to be effective at treating IMIDs. The present study aimed at evaluating the prevalence of the coexistence of selected IMIDs and other comorbidities, characterizing the patient population and assessing the use of anti-TNFs from a populational standpoint. METHODS: A cohort of patients who had received at least one diagnosis of rheumatoid arthritis (RA), ankylosing spondylitis, psoriatic arthritis, psoriasis (Ps), Crohn’s disease (CD), ulcerative colitis, or uveitis, between January 2005 and December 2009, was randomly selected from the Régie de l’assurance-maladie du Québec (RAMQ) databases.  The coexistence and temporality of the above diagnoses as well as other predefined chronic conditions were assessed.  Characterization and stratification according to demographics and anti-TNF use (use or no-use) were also performed. RESULTS: A total of 80,566 patients who had at least one diagnosis of an IMID were included in this cohort. The study population was on average 53.6 years old (SD : 21.3 years) and was in majority female (60,1%). Most common primary diagnoses were RA (33.4%), Ps (33.8%) and CD (22.8%) while 3.9% of patients had received at least one prescription of an anti-TNF medication. In this population, 9.1% of patients presented with one coexisting IMID diagnosis and 1.4% with 2 or more coexisting diagnoses. Among patients who had used an anti-TNF, 27.9% had one coexisting IMID diagnosis and 9.1% had 2 or more coexisting diagnoses. Other chronic comorbidities were found in 82.8% of patients. The most frequent comorbidities were hypertension (37.2%), cardiovascular diseases (22.4%), diabetes (16.7%) and osteoporosis (15.7%). CONCLUSIONS: Coexisting IMID diagnoses and comorbidities are often present in patients with IMID and greatly contribute to the burden of disease.