Infants with cystic fibrosis (CF) have disproportionately high secondhand smoke exposure. CF hair nicotine concentrations were determined by high-performance liquid chromatography-tandem mass spectrometry and plotted by age grouping (infants<1 year, children 1–5 years, children≥5 years). P=0.006 for infants vs children 1–5 years, p=0.002 for infants vs children≥5 years, via t-tests. Analysis of variance p=0.002. Nicotine concentrations were inversely correlated with age (r=−0.33, p=0.011, Pearson’s correlation coefficient), n=57. As a reference, active smokers have been reported to have median hair nicotine concentrations of 16.2 ng/mg hair.