This research was concerned with the theoretical investigation of the spray issued from a pressurised metered-dose inhaler (pMDI) and complements the experimental investigation of the pMDI spray using laser diagnostic techniques. The theoretical investigation of the pMDI spray consisted of constructing a model of the fluid flow through the pMDI actuator that was based on a quasi-steady-state separated flow analysis during a single actuation. Construction of a model of the resultant spray was based on the solution of the multiphase transport equations using computational fluid dynamics (CFD), with the theoretical results being validated against the experimental data obtained using phase-Doppler particle analysis (PDPA). The calculations were conducted for a hydrofluoroalkane (HFA) placebo formulation and the results suggested that the spray model successfully simulated the flow characteristics of the pMDI at the near-orifice measurement locations, thus validating the actuator flow model. However, the results produced by the theoretical spray model could only be considered as preliminary until further numerical analysis has been conducted.