The content of tobacco specific nitrosamines (TSNA) often increases in the cured burley tobacco leaves during storage. It was considered that TSNA would be formed when alkaloids react with the NOx gas generated from nitrite existing in cured leaves. We investigated the influence of the NOx gas generated from cured leaves on TSNA formation during storage. Three types of cured leaves with different nitrite and TSNA contents (average contents: low: nitrite nitrogen 2.8 µg/g and TSNA 1.1 µg/g; mid: 7.9 and 3.2 µg/g; high: 31.3 and 7.7 µg/g) were put into plastic bags separately and stored at 22 °C for 2 weeks, 1 month and 3 months. After the storage, NOx gas concentration in the bag and TSNA increases were detected. The higher nitrite content the leaves had, the higher NOx gas concentration and the greater TSNA increase they had. The leaves with a low nitrite content and the leaves with a high nitrite content were put into a bag together and stored at 30 °C for 1 month and 3 months. As compared with the low-nitrite leaves stored not with high-nitrite leaves, the NOx gas concentration in the bag and TSNA increase were higher. It seemed that the NOx gas generated from the high-nitrite leaves promoted TSNA formation in the low-nitrite leaves. It was considered that TSNA formation during storage could be suppressed by removing NOx gas. Cured leaves were put into a bag with activated carbon or zeolite, which are NOx gas adsorbents, and stored at 30 °C for 40 days. When the amount of activated carbon was 1% and that of zeolite was 10%, of the weight of the cured leaves, the NOx gas concentration in the bag was decreased and TSNA formation was suppressed.