Following an earlier study of the H-1 relaxation and NMR line shapes, we have carried out, selective one-dimensional and two-dimensional C-13 solid-state NMR studies that yield to detailed interpretation of the dynamics in form I, II, and III polymorphs of isotactic poly-l-butene. A specific defect diffusion along the side group is proposed to account for the temperature dependence of the C-13 spectra in form I. The backbone of the helix in forms II and III is shown to undergo large angle motions above the glass-transition temperature. High-resolution solid-state C-13 two-dimensional exchange NMR under magic-angle spinning with cross-polarization techniques demonstrates the existence of slow rotational jumps of the helices in form III with typical jump rates of about; 10 s(-1).