Along with the recent development of shipboard weapon systems of substantial firepower, considerable interest has risen in the design of light‐displacement, high‐speed combatant patrol boats. However, there has been an incorrect notion about patrol boats; “little boats have little problems.” From topside designers' point of view, little boats have many and big problems. Because of extremely limited shipboard topside space of this type ship, severe constraints are imposed for topside designers to effectively arrange shipboard combat systems, such as radars, fire control systems and communication equipment, to fully optimize the overall system performance and to sufficiently reduce electromagnetic hazards and interference (EMI). Recently, computer‐aided design techniques have been extensively utilized in combatant patrol boat topside design by making effective use of NAVSEA's topside design model (TDM), which allows for interactive design in graphically illustrated topside arrangements. Combat systems effectiveness is analyzed in terms of elevation plane optical coverages, radar line‐of‐sight (LOS) range detection, and omni‐directional antenna range prediction. The TDM algorithm includes the cumulative amplitude probability distribution of the HF communications range for the broadband fan and tuned whip antennas. The program is extended to analysis of the radiation pattern of directive antennas showing gain reduction principally due to blockage by superstructures. Finally, a set of candidate topside arrangements are proposed to the appropriate ship acquisition and design manager as feasible options to be pursued in the preliminary design phase.