Although the beneficial effects of caffeine on cognition and mood have been reported in a number of studies, relatively few studies have looked at the effects of caffeine in combination with other phytonutrients despite the fact that caffeine is seldom consumed in isolation. L-theanine is a naturally occurring amino-acid found in tea, and has been used historically as a relaxing agent (Haskell et al., 2008). Few have assessed the impact of l-theanine on cognition, but of those that have, the most interesting results were obtained when l-theanine was assessed in combination with caffeine (Haskell et al., 2008). It remains unclear what is underlying the reported effects.