N-nitrosonornicotine (NNN), a tobacco specific nitrosamine (TSNA) found in cured leaf, filler and smoke, is formed by nornicotine nitrosation. We previously demonstrated a ~75% reduction of cured leaf NNN content in burley and dark tobaccos having stable reduced convertor status (SRC) compared to Low Converter plants (LC). Here we present NNN data for burley and dark tobacco SRC and LC lines cured under normal conditions (control) and under conditions favourable for TSNA formation (experimental). SRC and LC burley were housed in a control barn and air cured according to recommended practices. Additionally, an experimental burley barn was packed with about ~1/3 more SRC and LC burley tobacco plants than the control barn and managed to retain high relative humidity during curing. For dark tobacco, SRC and LC lines were housed in a control barn and fire cured according to recommended practices. An experimental Dark barn was packed with SRC and LC Dark tobacco and cured at temperatures up to 173°F having open flames during curing. At the end of curing, leaf samples were collected and analyzed for TSNAs. SRC plants had ~63% and 64% less NNN than LC plants in control barns for burley and dark tobacco, respectively. NNN levels increased in SRC and LC tobaccos when cured in experimental barns compared to control barns. However, SRC NNN levels in experimental barns were ~76 and 61% lower relative to LC plants cured under identical conditions for burley and dark tobacco, respectively.