Sub-optimal adherence to inhaled maintenance therapy is common in children with asthma and Cystic Fibrosis (CF), resulting in poor disease control and increased exacerbations. Electronic monitoring with feedback has been shown to increase adherence in children with asthma by identifying and addressing intentional adherence barriers, and its use is now widespread in CF clinics in the UK. Medication reminders have been shown to be effective at addressing non-intentional adherence barriers in asthma, but have not been investigated in CF. This thesis aimed to investigate electronic monitoring with feedback and reminders to improve adherence and clinical outcomes in children with asthma and CF. Methods 90 children with moderate asthma were recruited to the STAAR study, and randomised to receive an electronic monitoring device (EMD) with 3- monthly feedback of data and alarms, or an EMD without feedback or alarms for a year. The primary outcome was the difference in Asthma Control Questionnaire (ACQ) score, from baseline to 3,6,9 and 12 months. Secondary outcomes were adherence, number of oral steroids required, lung function, hospital admissions, days off school and quality of life. The sample size was calculated using repeated measure analysis, with an MID for the ACQ of 0.5. 17 children were recruited to the Nebtext study and sent reminder text messages for 6 months. The outcomes were difference in overall, weekend and weekday adherence rates before and during the text message period. The sample size was the maximum number of children with CF attending clinic in the recruitment period. Results STAAR The mean [95% CI] difference in ACQ from baseline to 12 months was -1.14 [-1.6 to -0.7] in the intervention group, compared to -0.95 [-1.3 to -0.6] in the control group, with no significant difference between the two (P= 0.51). The mean [95% CI] adherence rate for the intervention group was 71% [63-77], vs. 49% [28-54] in the control group (p = < 0.001). The rate of exacerbations requiring oral steroids in the intervention group was 0.4 per 100 days, compared to 0.7 in the control group (p=0.008). The rate of hospitalisation was 0.03 in the intervention group vs. 0.13 in the control group (p = < 0.01). Nebtext The mean [95% CI] pre-text adherence rate was 80% [65-94], compared to 79% [62-95] during the text period. Conclusion Electronic monitoring with feedback and alarms is effective at reducing exacerbations and hospitalisations in children with asthma. The addition of reminder texts to existing electronic monitoring in children with CF does not further improve high baseline adherence rates.