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Barium oxide (BaO) and platinum (Pt) are the key components in lean NOx trap (LNT) catalysts. Previous work has demonstrated that highly dispersed and bulk-like BaO species have low-temperature (LT) and high-temperature (HT) release features for stored nitrogen dioxide (NO₂). To better understand the roles of both BaO and Pt, a series of BaO/Al₂O₃ and BaO-Pt/Al₂O₃ were prepared and used to investigate the release characteristics of stored NO₂. Two typical BaO-Pt/Al₂O₃ catalysts having 75% and 44% of dispersed BaO, respectively, were aged and used for both the static NO₂ storage and the dynamic NOx elimination by lean-rich cyclic reactions. Results showed that bulk-like BaO plays a lesser role in storing NO₂ than does dispersed BaO. Pt inhibits the formation of nitrates and thus decreases NO₂ storage capacity (NSC) as Pt can catalyze the release, particularly for NO₂ species stored on bulk-like BaO.