Does attending lectures improve student performance? Using novel attendance data, we examine statistically the relationships between attendance and performance for first-year and third-year students. The relationship is moderately positive: very high attendance is significantly associated with an improvement in performance over very low attenders of between 5.3% and 12.8%, depending on circumstances. Then we provide qualitative evidence from in-depth interviews with students about their views and motives regarding lectures. We find a range of reasons why attendance may be less than complete, and conclude that attendance is related to performance in complex ways.