Mastering pronunciation in EFL context, where direct access to native speaker is scarce, is a highly challenging objective for many language students in Iran. Stress as a suprasegmental feature, more specifically, poses its own problems, specially when suffixes are added to words. There are different types of suffixes, two of which are neutral (with no effect on word stress) and stress-moving (changing stress pattern). This research study intends to investigate the students' awareness of stress patterns when (stress-moving and neutral) suffixes are added to words. Thirty freshmen participated in this research. Their voices are recorded and analyzed. The use of Matched T-test shows that there is a significant difference in the level of difficulty of these two types of suffixes for the learners.