We report on the mutual relationships between reorientation and free volume in two poly(butadiene)s as seen by TEMPO and ortho-positronium (o-Ps) using ESR or PALS, respectively. The slow to fast transition of TEMPO in cis-trans-1,4-PBD and 1,2-PBD occurs at the similar characteristic ESR temperature T-50G with T-50G/T-g(DSC) = 1.22 for the former in contrast to T-50G/T-g = 0.85 for the latter. In spite of the T-50G < T-g relation an empirical rule tau(3) (T-50G) = 2.17 +/- 0.15 ns is confirmed suggesting that the main transition of TEMPO in 1,2-PBD occurs at the same free volume fluctuation independently of the physical state of the host matrix. (C) 2013 Elsevier B. V. All rights reserved.