Objective Use a standardized system to code parent–child interactions during respiratory treatments for cystic fibrosis (CF) and analyze relations between behaviors during treatments and medical regimen adherence. Methods A total of 15 families (53% girls; M age = 8.9 years; SD = 1.8) had three respiratory treatments recorded in the home environment and coded. Families provided six 24-hr recalls of child medical regimen activities, and electronic airway clearance time was recorded over 3 months to measure medical regimen adherence. Results Parent positive attention, instructions, and avoidance of negative statements were significantly related to child cooperation during respiratory treatments. Parental presence, positive attention, instructions, and child cooperation during treatments were related to higher respiratory adherence rates. Conclusions Direct observation methodology has led to effective nutritional adherence intervention for children with CF. These preliminary data demonstrate that an observational method could also be used to develop interventions to promote respiratory medication adherence.