This paper presents on-going research into the application of infrared (IR) thermography as a means of diagnosing the presence of delaminations in concrete structures. Infrared thermography, as a diagnostic tool, has demonstrated the potential to detect and visually display areas of delamination in concrete structures, offering a feasible supplement to the traditional techniques used for delamination surveys. However, the thermal gradients that develop in the concrete, and that are essential for the detection of the delaminations, are the result of the prevailing ambient conditions that surround the structure. Depending on the nature of these conditions, certain delaminations may be more visible than others while some may not be visible at all. Solar radiation has a significant effect on these thermal gradients and consequently, the temperature contrasts that develop between the areas of delaminated and intact concrete. This paper addresses the effect that solar radiation has on the ability of infrared thermography to detect and reveal areas of delamination in concrete structures. This effect has been studied by quantifying the temperature contrasts that developed at the surface of a concrete panel into which delamination type defects were intentionally embedded at different depths.