The profiles of resistance of ESBL(-) and ESBL(+) strains of Enterobacter cloacae were analysed and compared. 466 Enterobacter cloacae strains isolated from different specimens obtained from patients of big Warsaw hospital in 2004-2005 were investigated. By using the several phenotypic methods 33.5% of strains was identified as ESBL(+). ESBL(+) strains were significantly less susceptible then ESBL(-). These two groups differed mostly in susceptibility to aminoglycosides and fluoroquinolones, e.g. 65.5% of ESBL(-) strains were susceptible to gentamicin, compared to only 25.0% ESBL(+), in case of ciprofloxacin 59.0% of ESBL(-) were susceptible whereas only 25.0% of ESBL(+) strains. The percentage of ESBL(+) grew from 26.4% in 2004 to 40.4% in 2005, whereas a tendency of growing susceptibility to aminoglycosides and fluoroquinolones was noted among all E.cloacae strains. Susceptibility to combinations of piperacillin or ticarcillin with beta-lactamase inhibitor was rather low among ESBL(+) strains.