The use of online lecture recordings as a supplement to physical lectures is an increasingly popular tool at many universities. This paper combines survey data with student record data for students in a "Microeconomics Principles" class to examine the relative effects of lecture attendance and online lecture recordings. The main finding is that students using the online lectures as a substitute for attending lectures are ultimately at a fairly severe disadvantage in terms of their final marks. Moreover, students attending few face to face lectures do not close this gap by viewing more lectures online. In contrast to this, students who attend the majority of lectures in person do receive a benefit from additional use of the lecture recordings. The results provide empirical evidence that, when used as a complementary tool, lecture recordings are a valuable supplement for students. However, when used as a substitute to attending lectures, lecture recordings provide no additional benefit. (Contains 2 figures and 3 tables.)