Short measures are commonly used when conducting research involving emotions. However, obtaining appropriate estimates of reliability for short measures is traditionally problematic and is a reoccurring concern in emotion research. To address this issue, we compare the within-session test-retest and factor analysis methods for estimating the reliability of items in the Positive and Negative Affect Schedule–Expanded Form. Results indicate that within-session test-retest (rXX(d)) estimates outperform the factor analysis method by demonstrating stronger relationships with item properties relevant to reliability and validity-related criteria. In addition, rXX(d) estimates appropriately generalize across samples with various instruction stems and prevent corrections for attenuation greater than 1.00. Therefore, we encourage researchers to use the corresponding average item-level rXX(d) estimates reported here to correct for attenuation when examining single items from the Positive and Negative Affect Schedule–Expanded Form if a test-retest design is not feasible.