Background: Researchers working with children and young people with life-limiting conditions and life-threatening illnesses (CYP with LLC/LTIs) frequently identify research ethics committees (RECs) as a barrier to their research. However, little is known about what concerns RECs in research with CYP with LLC/LTIs.
Aim: To explore the concerns expressed by RECs when reviewing studies involving CYP with LLC/LTIs, and how researchers address these concerns. 
Methods: Data included REC-research team correspondence, specifically: REC decision letters, meeting minutes and researcher response letters. Analysis was conducted using content analysis. 
Results: REC decision letters and meeting minutes were available for 77 studies. For 27 studies, response letters from researchers were available. Within the REC decision letters, 298 concerns were raised, 162 of which were agreed to by chief investigators. In addition to general REC concerns relating to research methodology, information sheets, and formatting errors, there were concerns specifically relating to CYP with LLC/LTIs, such as the need for clinical team involvement in recruitment and appropriate ages for consent/assent. 
Conclusions: Commonly, studies involving CYP with LLC/LTIs require changes before they are approved by RECs. Many of these changes, including formatting issues can be resolved easily with careful review from the research team and peers before submission. More detailed consideration is needed for the other concerns, such as consent procedures and recruitment strategies, to ensure the needs of CYP with LLC/LTIs are adequately considered and to ensure that these concerns do not present a barrier to getting research with this population underway. 
Funding:The authors disclosed receipt of financial support from The National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research & Care,Great Ormond Street (GOS) Children's Charity, NIHR-GOSH BRC &The True Colors Trust.

Challenges in Receiving Research Ethics Committee Approval for Studies Involving Children and Young People with Life-limiting Conditions and Life-threatening Illnesses: An Analysis of Research Ethics Committee Minutes and Correspondence with Principle Investigators