Smartphone use has become ubiquitous among college students, with several reports suggesting that students spend over six hours per day on their devices. However, the potential effects of extended engagement with of smartphones on cognitive ability and academic achievement are not well understood. In this research we compared problematic self-report smartphone use in two groups of undergraduate students (STEM and humanities). The groups had very similar demographics in terms of age and sex, and similar mean GPA scores. However, there was a strong negative association between problematic smartphone use and GPA in the STEM students, which was not seen in the humanities students. Furthermore, this association in the STEM students was found to be related to self-reported executive functions- impulse control and sustained attention. We speculate that problematic smartphone use may cause academic problems disproportionately for STEM students because it reduces cognitive resources, which are particularly important to achieve higher grades in fields such as science technology engineering, and medicine.