Aryl hydrocarbon receptor (AhR)-regulated cytochrome P4501A1 (CYP1A1) and P4501B1 (CYP1B1) have been shown to metabolically activate some carcinogens. In the present study, we utilized the real-time reverse transcription-polymerase chain reaction (RT-PCR) assay to compare AhR, CYP1A1 and CYP1B1 mRNA levels in peripheral leukocytes from 42 lung cancer patients and 59 non-cancer subjects. We found that CYP1A1 and CYP1B1 levels, but not AhR, were significantly higher in patients than in non-cancer subjects. After stratified by gender, CYP1A1 levels were significantly higher in female patients than in female controls. After controlling for age, smoking status and gender, lung cancer patients were more likely to be CYP1B1 high expressers (P < 0.05). Neither AhR nor CYP1A1 levels was associated with lung cancer incidence. Leu-Val polymorphism of CYP1B1 was not associated with lung cancer risk in our study. These data indicated that CYP1B1 mRNA levels were elevated in peripheral leukocytes of lung cancer patients.