Background: Priority setting is important, but inevitable difficult task for decision makers. Many priority-setting principles have been proposed for allocating resources and these different principles may have different weights for prioritizing an intervention. This thesis discusses these dilemmas of priority-settings particularly among adolescents in general and adolescents with post-traumatic stress disorder (PTSD). Objective: The objective of this thesis was to find out the condition under which an intervention treating adolescents for post-traumatic stress disorder would be prioritized with regard to severity, clinical effectiveness and cost-utility and to observe if there are any discrepancies in priorities from these principles. Method: Two sources of data were used in the study; one with the randomized control trial (RCT) among adolescents with PTSD and other a systematic literature review on cost-utility studies. The adolescent of PTSD group was included as a case and the dataset was discussed in relation to a review of cost-utility studies among adolescents. Results: The intervention for PTSD would be prioritized if information on clinical effectiveness and costs were available in addition to severity. The review reported different rankings of interventions according to severity, clinical effectiveness and cost-utility however; there was a strong correlation in the rankings of QALY gain and incremental cost-effectiveness ratio (ICER). Furthermore, the study found that broader societal viewpoints in cost-utility studies avoid underestimation of costs and consequences for at least some of the diseases. There were also some interventions that would not be prioritized at all, even if they produce greater QALY gain, are cost-effective and have high demand in the society. Conclusion: There should be evidence of clinical effectiveness and cost-effectiveness of interventions for decision makers to discuss priority setting for PTSD group. Even, if all information is known, it was found that multiple criteria of priority setting principles would make decision making process more complex. The result showed variations in ranking of interventions with regard to severity, clinical effectiveness and cost-utility in adolescents. The key challenge for policy makers would be to find a way to explain how these differences occur and how these variations could be balanced.