Treatment adherence in cystic fibrosis (CF) is often poor, however, less is known about adherence to pancreatic enzymes, a critical component of the CF treatment regimen. Parent caregivers often report elevations in depression, and parental depression may adversely affect children's adherence. This prospective study evaluated adherence to pancreatic enzymes in 83 patients (1-13 years) . Adherence was measured across 3 months with electronic pill-caps . Weight was measured at baseline and a 3-month follow-up. Parental depressive symptoms were evaluated by using the Center for Epidemiologic Studies Depression Scale (CES-D). Adherence to pancreatic enzymes was 49.4% ± 3.4%. Adherence was higher at school (94.4% ± 6.1%) than at home (42.3% ± 3.1%), and higher for toddlers (50.6% ± 5.2%) than for school-aged children (37.5% ± 3.7%). Parents reported high rates of depressive symptoms (30% in the clinical range, 18% with moderate symptoms). Children of parents with symptoms of depression versus those without were less adherent (34.8% ± 4.5% vs 48.5% ± 4.1%), and adherence to enzymes was significantly related to 3-month weight outcomes. Average gain in weight z scores across 3 months was 0.5 ± 0.2for children who were >50% adherent and -0.1 ± 6.1for children who were <33% adherent. Parental depression had a signifcant, indirect effect on weight via adherence (-0.005 ± 0.003 gain in weight z score per CES-D unit ). High rates of parental depressive symptoms, coupled with its negative effects on adherence, suggest that measuring and treating parental depression may improve children's adherence to therapy.