This thesis considers a common healthcare challenge of planning capacity for a system of care where patients receive multiple treatments sessions from multiple resources. As a case study of this more general problem, we considered the particular context of a capacity planning model for the Mood and Anxiety Program at The Ottawa Royal Health Centre (referenced as The Royal for simplicity) where a new service system known as CAPA (www.capa.co.uk) is being implemented to enhance the mental care provided to its patients. In order to develop the capacity planning model, we have created a simulation model using the Arena simulation software. We have also used the ABCMod Framework as the modeling methodology. The ABCMod is an activity based conceptual modelling framework that provides a set of guidelines as to how to build a conceptual model including its structural and behavioural aspects as well as a collection of constructs which include inputs, outputs and parameters among others. The ABCMod framework tools are expected to facilitate the model validation with project stakeholders. A series of scenarios relevant to The Royal were modeled and analyzed in order to determine how best to manage capacity so certain performance goals within the CAPA system implementation are met. These scenarios determine the service level The Royal can provide with its current capacity and also the amount and distribution of resources that is required to achieve its goals under the CAPA system. As a result of our simulation runs, we defined the policy implications for The Royal in order to achieve its targets and successfully implement CAPA. Additionally, through the application of the ABCMod framework and standard process mapping tools, we were able to reach a consensus and validate our modeling approach with the project stakeholders at The Royal. Our model could be adapted to other settings in which multiple resources provide a series of sequential interventions to clients.