  We derive relations between polarized transverse momentum dependent
distribution functions (TMDs) and the usual parton distribution functions
(PDFs) in the 3D covariant parton model, which follow from Lorentz invariance
and the assumption of a rotationally symmetric distribution of parton momenta
in the nucleon rest frame. Using the known PDF $g_{1}^{q}(x)$ as input we
predict the $x$- and $\mathbf{p}_{T}$-dependence of all polarized twist-2
naively time-reversal even (T-even) TMDs.
