In x-ray computed tomography (CT) spiral/helical scanning is achieved by continuous and simultaneous source rotation, object translation and data acquisition. In medical imaging, fan-beam spiral CT has replaced conventional incremental CT. Also, cone-beam spiral CT is feasible and advantageous is important applications. In this paper, resolution characteristics, protocol optimization, and image restoration are discussed in fan-beam spiral CT. Then, generalized Feldkamp cone-beam reconstruction is described is spiral geometry. Based on Snyder's iterative deblurring theory, a unified iterative algorithm is reported to handle incomplete cone-beam data. Finally, several future possibilities in spiral CT are mentioned.