Selecting a portfolio of projects is essential for organizations to sustain and develop their businesses and increase profitability. While creating a suitable portfolio, the opinions of the employees in the organization's hierarchy about alternative projects can improve the decision process. In this paper, we structure the information technology/business development (IT/BD) project portfolio selection problem as a hierarchical group decision-making setting. Our aim is to process information provided from a large number of employees participating in the decision-making process and prevent the dominance of a single decision maker or biases due to irrelevant evaluations. A weighted cumulative belief degree approach is proposed for aggregating the evaluations of the decision makers and experts on the projects and on the importance weights of the criteria. We conduct a real-life case study in an organization in the automotive sector. The application shows that the proposed approach can enable getting evaluations from a large organization with less time and provides diverse results based on the several satisfaction levels.