This work presents a novel computer-aided design (CAD) tool for the design of tapered leaky-wave antennas (LWAs) in hybrid waveguide printed-circuit technology. The software package is composed of several tools, which are connected together to provide a semi-automated step-by-step design procedure. The design procedure is presented and the different tools are described, together with the involved theory, leading to the design of tapered LWAs. A practical taper design is performed, and comparisons with simulations using commercial software (HFSS) are presented for validation purposes. Due to the full-wave nature of the technique used in the analysis engine, excellent agreement is shown between the proposed 2D-based approach, and 3D HFSS results. Also, the analysis procedure is fast, thus leading to semi-automated designs that are not affordable with common 3D optimization techniques. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.