This paper presents for the first time theoretical estimates of the non-local thermodynamic equilibrium (NLTE) populations for vibrational states of the N,O and CH, molecules in the stratosphere and mesosphere. For N,O the nighttime heights of the transition to NLTE decrease with vibrational energy from about 70 km for the (01'0) state to about 55 km for the states excited in the v3 mode. For daytime the vibrational temperatures of the (OO"1) state and of higher N,O states far exceed those for nighttime. For the N,O (02"1, 02'1, 1O"l) states the daytime NLTE layer extends throughout the entire stratosphere. For the first excited states of the CH, \t2 and vq modes the transition to NLTE occurs near 60 km. The vibration-vibration (V-V) energy exchange with N, and 0, is important in the mesosphere for populating the N,O and CH, states, respectively. Using the HNO, molecule as an example, we propose a simple way of estimating roughly the NLTE population of vibrational states of polyatomic molecules when data on the rate constants of vibration-translation (V-T) and V-V energy transfers are lacking. For the HNO, states not higher than the v,-state a speculative estimate yields about 50 km as the lower limit for the heights of the transition to NLTE.