Exhibit 99.1 Diluted earnings per share attributable to Packaging Corporation of America shareholders | | | | Three Months Ended | | | | | --- | --- | --- | --- | --- | --- | --- | | | | | June 30, | | | | | | 2025 | | 2024 | | Change | | | Reported Diluted EPS | $| 2.67 |$ | 2.21 | $| 0.46 | | (1) Special Items (Income)/Expense | | (0.19) | | — | | (0.19) | | (2) (3) Diluted EPS excluding Special Items |$ | 2.48 | $| 2.20 |$ | 0.28 | For descriptions and amounts of our special items, see the schedule ...