Absenteeism has been a common and very extended problem in university spheres for several years. This problem has become a permanent feature in academic studies in general, yet it has received scarce empirical research attention. This work is focused on the analysis of the factors that determine university absenteeism. It evaluates a series of reasons or causes that prevent students from attending lessons regularly both if they are reasoned (involuntary absenteeism) or not (voluntary absenteeism). This study is based on a sample of 139 students in the third year of the Degree in Tourism. Our analysis shows us that absenteeism is a complex and multifactorial phenomenon. Seven determining factors of absenteeism were obtained: efficiency, teaching style, academic interest, teaching contents and format, classmates influence and fears, imponderables and convenience. The dimension "Teaching Style" is given the highest average score.