Field effect transistors (FETs) with channel material made of a dense array of perfectly aligned carbon nanotubes (CNTs) have been claimed to replace silicon FETs in various applications, including energy efficient high-frequency front-end circuits in communication systems, such as highly linear and low-noise amplifiers. CNTs are especially suitable for radio frequency (RF) electronics, mainly owing to their high carrier mobility, large saturation velocity and small intrinsic capacitance, which are crucially important for excellent RF-performance. To support the development of competitive RF-CNTFETs, numerical device simulations are required to provide a fundamental understanding of the impact of various physical effects on the device behavior. Additionally, the optimization of the device design is guided by these device simulations. They also provide a reference for compact models, which are required for exploring the potential of RF-CNTFETs in circuits and for benchmarking with incumbent and other emerging technologies.