Concentration distributions of benzene (determined by PTR-MS) in exhaled breath of lung carcinoma patients (smokers: red; non/ex-smoker: magenta) and healthy volunteers (smokers: blue; non/ex-smokers: green). The concentration is shown in logarithmic scaling. Benzene concentration is increased in the subgroups of smokers and therefore a marker for smoking behavior. The median values for benzene in human breath have been determined as follows: CA-patients-non/ex-smoker 0.9 ppb, control-non/ex smokers 1.1 ppb (significant difference according to Kruskal-Wallis test: p-value 0.002); CA-patients-smoker 2.9 ppb, control-smokers 2.4 ppb (no statistical significant difference according to Kruskal-Wallis test: p-value 0.469). The difference in smoking behaviour (between smoker and non/ex-smoker) is statistically significant for the control group (p-value < 1*10-5) as well as for the CA-patients (p-value < 1*10-5).