The objective of the present study was to verify which physiological (percentage of maximum oxygen consumption - %VO2 or percentage of maximum heart rate - %HR) or psychological (ratings of perceived exertion - RPE) variable is the best predictor of affective responses during continuous (CT) and interval (HIT) exercise sessions. Fourteen men underwent 3 exercise sessions on the treadmill. In the first session, a graded exercise test was performed to determine the maximum HR, peak VO2, and the respiratory compensation point (RCP). Then, participants performed the CT and HIT exercise in a counterbalanced order. The HIT session consisted of 2 min stimuli with an intensity of 100% of peak VO2 interspersed with periods of passive recovery. The average intensities of both exercise sessions were equalized at 85% of RCP. Linear regression analyses of both exercise sessions showed higher prediction values of RPE (CT - R2=.54, p<.01; HIT - R2=.68, p<.01) compared to %VO2 (CT - R2=.04, p=.08; HIT - R2=0.3, p=.12) and %HR (CT - R2=.07, p=.02; HIT - R2=.05, p=.05). Additionally, the results of the linear regression analysis between the Feeling Scale and physiological variables were not significant, indicating that the slope of the regression analysis was not different from zero. These results may be explained by the conscious mental processing required for the manifestation of both the RPE and the affective responses. In conclusion, the affective responses seem to be modulated not only by the intensity of exercise but also mostly by how the individual perceives this intensity.