 Synthetic photochemistry carried out in classic batch reactors has, for over half a century, proved to be a powerful but underutilized technique in general organic synthesis. Recent developments in flow photochemistry have the potential to allow this technique to be applied in a more mainstream setting. This review highlights the use of flow reactors in organic photochemistry, allowing a comparison of the various reactor types to be made. This article was authored by Jonathan P. Knowles, Luke D. Elliott and Kevin I. Booker-Milburn.