The capability for biofilm and quorum-sensing (QS) signaling production among Pseudomonas aeruginosa isolates were evaluated. A total of 231 isolates were recovered from sputa of cystic fibrosis (CF, n = 104) and non-CF (non-CF, n = 127) patients. One hundred ninety-seven (85.3%; 95% CI 80.1-89.3%) were biofilm producers and 157 (68%; 95% CI 61.7-73.6%) were weak QS-producing. No difference was observed between CF and non-CF isolates regarding the ability to produce biofilm and QS-signaling. Interestingly, the degree of QS production appears to be related to the degree of biofilm production. Thus, blocking QS pathways may be crucial in the prevention and treatment of biofilm-related infections.