At the nanoscale, zinc oxide forms in many different shapes, the dimensions of which are often closely related to specific properties. Although much attention is focussed on finding methods for controlling the morphology, explanations of phenomena such as the change in crystallographic orientation of the principle axis of one-dimensional nanostructures (with size) are still largely empirical. We have used a shape-dependant thermodynamic model to identify the relationship between size, structure and orientation in zinc oxide nanobelts, and present results showing that growth in the +/-[12 10] direction is a decisive factor in determining the orientation. Published by Elsevier B.V.