Introduction: Studies in critically ill children within paediatric intensive care units (PICU) experience an ethical dilemma in that life-saving interventions may not allow time for prospective consent to be obtained from legal guardians. In certain circumstances there is insufficient time to consent before the intervention is performed. Objectives/Aims: This descriptive analysis aimed to identify the most common challenges to obtaining prospective consent in a randomised controlled trial (RCT) conducted within a tertiary PICU and examine how these challenges may affect recruitment of suitable study participants. Methods: Data pertaining to consent was collected at the recruitment stage of a large RCT conducted within Queensland Children’s Hospital PICU. Data included whether recruitment was via prospective or deferred consent. In the deferred consent group, researchers specified whether the parent had a prior awareness of the study and recorded reason/s why if the parent was unaware. Results: At the 2-year mark, results indicated 16% (n=49) of participants were recruited using prospective consent, with the remainder (n=252) recruited using deferred consent. Eighty-nine parents in this group had no knowledge of the study prior to the intervention occurring. Sixteen (18%) parents were too distressed to approach, 61 (69%) parents were not at the bedside, and 19 (21%) patients experienced a rapid or unexpected deterioration. Eight had “other” or “unknown” reasons recorded by research staff. Conclusion: Commonly cited challenges to prospective consent included the emergent nature of the intervention, the absence of a legal guardian, and parental distress indicating a lack of capacity to provide informed consent. This information highlights the need to consider alternate methods of consent in clinical trials within PICU. Although it should be the preferred option, prospective consent is not always possible. Deferred consent was well accepted with an absence of parental complaints regarding the consent process.