BACKGROUND Pseudomonas aeruginosa is known as an opportunistic pathogen responsible for nosocomial infections. Multidrug (MDR) resistance bacteria are considered as a worldwide issue. The current research goal to investigate the antibiotic susceptibility pattern in Extended Spectrum beta-lactamase and non Extended Spectrum beta-lactamase producing P. aeruginosa clinical isolates. METHODS A total of 76 P.aeruginosa clinical isolates were collected from Milad hospital in Tehran, Iran, during 8 months period in 2012. P.aeruginosa clinical isolates were subjected for ESBL production by phenotypic methods. The antibiotic susceptibility patterns were identified in ESBL and non-ESBL P. aeruginosa by MIC. RESULTS our results demonstrated that 76.3% (n =58) isolates were resistant to more than three antibiotics and classified as MDR. The majority of MDR strains were found in ESBL producer P. aeruginosa. ceftazidim as 3rd generation of cephalosporins, ciprofloxacin, Ticarcillin and aztreonam were found as a base for definition of MDR in the current research. The effectiveness antibiotics against ESBL and non-ESBL were meropenem and amikacin, respectively. CONCLUSIONS based on our knowledge obtained from results, both ESBL and non-ESBL P. aeruginosa were resistant to extended antibiotics and this is a major health care problem. On the other hand, MDR strains more identified in ESBL producer P .a eruginosa. Also, carabapenem resistance observed in non-ESBL producer strains. Hence, it is recommended that the MDR strains should be following up. the prescription of ceftazidim, ciprofloxacin, Ticarcillin and aztreonam should be limited.