Project supplier firms are solution providers. A solution may consist of a core project delivery with specific service contents, and/or of separate service deliveries. This paper analyzes the role of services in the business model of a project-based firm. The empirical study focuses on the business models of five project supplier firms, and on the relationship of the core project delivery and deliveries of different services to the business model. We identify six different ‘impact types’, each of which illustrates a different way in which services can affect the business of a project-based firm. The impact types are: customer entry, customer value, competitive advantage, delivery efficiency, service business, and innovation and learning. Our empirical study suggests a wealth of different service offerings and their complex relationships with the business model and revenue generation logic of a project supplier firm. We conclude with several distinctive findings that relate to how services are seen in the firms’ businesses, with these approaches obviously serving as enablers or barriers to good business performance. The paper suggests further research on specific areas related to the overall theme of project and service business.