Background: Non-medical data such as patients’ and caregivers’ time can be relevant to assess therapeutic strategies. For chronic pediatric conditions, patients’ and caregivers’ time spent in seeking and providing care (i.e. indirect cost in an economic evaluation) can be significantly different depending on the treatment arm. In order to explore methods to collect information on care burden for caregivers and patients, we investigated whether or not a patient diary provided additional information compared to retrospective investigator-led interviews and whether a diary filled intermittently produced more or less information than a continuous diary. The main objective of this study was to identify which type of data collection was most effective to measure caregivers’ time and estimate indirect treatment costs over a 9-month period. Methods: Start-In! is a randomized controlled trial comparing the efficacy of three strategies of real-time continuous glucose monitoring (CGM) for 12 months in children and adolescents with type 1 diabetes. We designed an ancillary study to assess methods of patients’ and caregivers’ time (indirect costs): data entered was retrospectively in the case report form by investigators during quarterly follow-up visits, with the help of diaries filled prospectively by children or caregivers either continuously or intermittently. Data about absence from school and work as well as caregivers’ time for diabetes care were collected and comparisons carried out between the three collection methods. Results: At the end of the 9-month study, 42% of study participants failed to return their diary. For the diaries that were received, less than 10 were contributive on top of the information entered on 82 patients directly by investigators .Based upon this information, we calculated that over 9 months, caregivers lost on average 3.9 days of working time, (€786), and 4 days of personal time, i.e. the equivalent of €526, as well as around 15 minutes of care per day, i.e. the equivalent of €1,700. Conclusions: Data collection by investigators during quarterly visits cannot be replaced by a diary. The completion of diaries appeared to represent an important additional burden to children and their caregivers and provided limited additional information compared to investigators ‘entries in the CRF. Trial registration: Start-In! trial registry name: Study of Insulin Therapy Augmented by Real Time Sensor IN Type 1 Children and Adolescents (START-IN!). ClinicalTrials.gov Identifier: NCT00949221. Registered on July 30, 2009.