Abstract Background Substance use is a recognized Paediatric health care issue. More than 9 in 10 individuals receiving treatment for substance use disorders report that their first use of substances occurred by young adulthood. The Canadian Institute for Health Information reported that 5% of hospital stays among Canadian youth in 2017-2018 were related to harmful substance use. In a study of youth with a first-time emergency department visit for a mental health problem between 2010 and 2014, most visits were due to substance related disorders. Despite this, little is known about practices relating to substance use in children's hospitals. Objectives 1. To describe how adolescents who present to Paediatric hospitals with substance use disorders or substance-related health issues are identified, assessed, and treated. 2. To identify best-practices that can inform national standards of care. Design/Methods An online questionnaire was utilized to obtain information on: 1. Clinical practices in the emergency department, inpatient services and ICU; 2. Hospital policies and practice guidelines; and 3. Hospital and community programs and resources. Recruitment emails were sent to hospital leaders (CEO or equivalent) at all 13 Paediatric hospitals. Leaders were asked to identify one individual to complete the survey on behalf of their hospital with input from relevant stakeholders in the various clinical areas. The survey was developed iteratively by a national group of 9 adolescent medicine clinicians and 2 Paediatric trainees. The survey was piloted at a single Paediatric hospital and refined. The survey was administered via RedCap technology. Results Survey response rate was 70% (9/13 hospitals). The mean number of contributors to each survey was 9 (range of 1-35). Overall, few hospitals utilized best practices consistently. There was inconsistency in the use of validated screening tools, use of clinical practice guidelines for monitoring and ongoing care and prescribing of nicotine replacement therapy and opioid agonist therapy. These inconsistencies were noted within each clinical setting (emergency department, inpatient services, and ICU), across services in each hospital, and between hospitals. With respect to hospital services, 5/9 had some type of consult team related to substance use (e.g., adolescent medicine), 4/9 had specialized substance use outpatient services, and 2/9 offered partial hospitalization/day treatment for patients with substance use issues. Local community-based substance use resources were identified as insufficient to address needs by 8/9 hospitals. Conclusion Inconsistencies in the care of adolescents with substance use disorders or substance-related health issues highlights the need for national guidelines for Paediatric hospital-based assessment and care, and enhanced coordination between services and systems of care for this patient population.