Growing demand for high quality diesel is being driven principally by increasingly stringent legislation governing the composition of liquid transportation fuels and, amongst the various alternatives to meeting this demand, Fischer-Tropsch (F-T) based Gas-to-Liquids (GTL) processing is recognized as an industrially proven and economically competitive route. Furthermore, it is generally accepted that for this purpose, GTL processing is most effective when comprising an F-T synthesis driven to wax production, followed by hydrocracking to produce the middle-distillate products. By means of comparison between refinery and F-T GTL hydrocracking feedstocks, and demonstration of the poor applicability, to F-T wax processing, of catalysts optimized for refinery feedstocks, this paper argues that a significant opportunity exists for optimization of the wax hydrocracking step and also for an overall improvement of F-T based GTL processing.