Network capacity investigation has been intensive in the past few years. A large body of work on wireless network capacity has appeared in the literature. However, so far most of the effort has been made on two-dimensional (2-D) wireless networks only. With the great development of wireless technologies, wireless networks are envisioned to extend from 2-D space to three-dimensional (3-D) space. In this paper, we investigate the throughput capacity of 3-D regular ad hoc networks (RANETs) and of 3-D nonhomogeneous ad hoc networks (NANETs), respectively, by employing a generalized physical model. In 3-D RANETs, we assume that the nodes are regularly placed, while in 3-D NANETs, we consider that the nodes are distributed according to a general Nonhomogeneous Poisson Process (NPP). We find both lower and upper bounds in both types of networks in a broad power propagation regime, i.e., when the path loss exponent is no less than 2.