Imipenem-resistant Pseudomonas aeruginosa is a leading cause of hospital-acquired pneumonia. Aiming to determine the risk factors associated for hospital-acquired pneumonia due to imipenem-resistant Pseudomonas aeruginosa, we undertook a retrospective case-case-control study. Patients admitted to a 14-bed medical-surgical intensive care unit from a university-affiliated hospital with hospital-acquired pneumonia caused by imipenem-resistant Pseudomonas aeruginosa strains and by imipenem-susceptible Pseudomonas aeruginosa strains were matched to control patients by time under risk and comorbidities. A total of 58 resistant cases, 47 susceptible cases and 237 controls were evaluated. The risk factors independently associated to hospital-acquired pneumonia caused by imipenem-resistant Pseudomonas aeruginosa were: duration of hospitalisation, Acute Physiological and Chronic Health Evaluation II score, male gender receipt of haemodialysis, receipt of piperacillin-tazobactam and receipt of third-generation cephalosporins.