Despite the potential benefits highlighted in the literature, the widespread adoption of Demand Responsive Transport services remains limited. Integrating passenger and freight transport within the same DRT system could improve its profitability and market suitability, particularly in low-demand areas. The study proposes a model where low-capacity vehicles transport both passengers and parcels within a specific service area, prioritising passenger requests while accommodating deliveries during idle times. This approach aims to optimise resource utilisation and increase revenue without requiring passengers to act as crowdshippers, thereby avoiding administrative and behavioural barriers. An agent-based model is developed to simulate the operation of the integrated service, with passengers and parcels sharing the same vehicles. The model allows for the adjustment of various parameters within a synthetic simulation environment, enabling the evaluation the benefits of prioritising passenger requests compared to scenarios where passengers and freight are given equal priority. By varying input parameters such as the extension of the service area, the ratio between demand densities of travellers and parcels, and the priority discipline adopted during the reservation processes, the results provide useful suggestions for planning integrated passengers-freight DRT services across diverse scenarios, offering practical recommendations for improving the efficiency and viability of such systems.