Single-walled carbon nanotubes (CNTs) possess physical properties (strength, flexibility, conductivity or semiconductivity) that make them attractive for use in applications from material science to nanotechnology. Understanding the ways in which CNTs react and the differences in reactivity between conductive and semiconductive CNTs is an important step in developing strategies for functionalizing CNTs. Previous work has demonstrated the usefulness of the Clar Valence Bond (VB) model in understanding the electronic differences between conductive and semiconductive CNTs. One potential use of CNTs that has drawn attention recently is hydrogen storage. In this work, the Clar VB model is used as a starting point for understanding and predicting the lowest energy (most favorable) isomers that result from the step-wise hydrogenation of CNTs.