This study is an attempt to develop a preliminary composite fuselage sizing tool for the decision making process utilizing analytical structural analysis equations and a bottom-up cost approach to estimate weight and cost. Previous research by several authors and companies is reviewed in order to define the knowledge gaps that the project is going to fill. The objectives of this project are divided into two directions. The first one is the weight and cost fuselage design, and the second, is the weight and cost optimization process. After examining the existing literature both from academia and industry a different approach is proposed for each sector. In the structural design an analytical based model is proposed to assess the components integrity while cost equations for fully learned manufacturing processes are used based on the Advanced Composites Cost Estimation Manual (ACCEM). An experience-driven optimization algorithm is proposed afterwards, taking into account manufacturing considerations and design rules of thumb. By combining these tools, a general tool for fuselage design that is completely suited for the preliminary design phase is proposed. Τhe trade-off studies can provide important knowledge on the effect of different decisions and establish new design guidelines. The study concludes that an increase of the number of stiffeners and frames, in a fuselage structure, leads to a general decrease in weight and an increase in manufacturing cost. The addition of more stringers or frames after a certain level leads to an increase in weight, while the cost follows the same trend. The manufacturing constraints and the design rules-of-thumb applied lead to an increase in structural weight. Finally, the comparison between skin-stiffened and sandwich designs, shows that the weight saving potential is comparable for both configurations, and the cost saving potential is higher for the sandwich design.