Bourdon manometry was used to obtain the total pressure variation versus temperature of the chemical system describing the transport of niobium diselenide by iodine. The existence of the niobium triiodide NbI 3 has been shown in the chemical vapour transport (CVT) equilibrium process: NbSe 2( s) + 3 2 I 2( g) = NbI 3( g) + Se 2( g) . Experimental results, in the 900–1150 K temperature range, have allowed us to determine the equilibrium constant of this transport reaction. A kinetic study of CVT of NbSe 2 by iodine has been realized, in a multizone furnace with a three-zone profile, and is compared to a previous study in a two-zone profile. The influence of transport time and thermal gradient used has been studied: it confirms the previous results and shows a disconnection, foreseen by the three-zone technique, between thermodynamic and hydrodynamic regines in the vapour phase. The predicted diffusive regime is verified, by comparison to the work of Arizumi et al.