Objectives: Consumer satisfaction is considered one of the most important measures of service quality in child mental health; however, there is limited understanding of factors that influence satisfaction. The objective of this study was to investigate key factors influencing satisfaction with care (SWC) in ADMiRE, a specialist service for young people (YP) with attention deficit hyperactivity disorder (ADHD). Methods: Parents/carers (n = 67) and YP > 9 years (n = 44) attending ADMiRE completed an anonymous Experience of Service Questionnaire (ESQ), a quantitative/qualitative measure of service user satisfaction. Parents/carers also completed symptom severity rating scales. Data were analysed to determine (i) overall SWC, (ii) the relationship between parent- and youth-reported SWC and (iii) the impact of symptom severity on SWC. Thematic analysis of qualitative ESQ data was completed. Results: Parents/carers were significantly more satisfied than YP (p = 0.028). Symptom severity did not impact significantly on parent/carer satisfaction. YP with severe hyperactive/impulsive and inattentive ADHD symptoms were significantly less satisfied with care than those with less severe ADHD symptoms (p = 0.022 and p = 0.017 respectively). Factors related to the therapeutic alliance were identified as being particularly important to both parents/carers and YP. Conclusions: This is the first Irish study that has investigated the impact of symptom severity on service user satisfaction in a child mental health service. The results highlight the different perspectives of YP and parents and provide novel insights into the impact of symptom severity on service user satisfaction. The importance of the therapeutic alliance should not be underestimated in future development of services.