  We compare results of $k_t$-factorization approach and next-to-leading order
collinear-factorization approach for dijet correlations in proton-proton
collisions at RHIC energies. We discuss correlations in azimuthal angle as well
as correlations in two-dimensional space of transverse momenta of two jets.
Some $k_t$-factorization subprocesses are included for the first time in the
literature. Different unintegrated gluon/parton distributions are used in the
$k_t$-factorization approach. The results depend on UGDF/UPDF used. For
collinear NLO case the situation depends significantly on whether we consider
correlations of any two jets or correlations of leading jets only. In the first
case the $2 \to 2$ contributions associated with soft radiations summed up in
the $k_t$-factorization approach dominate at $\phi \sim \pi$ and at equal
moduli of jet transverse momenta. The collinear NLO $2 \to 3$ contributions
dominate over $k_t$-factorization cross section at small relative azimuthal
angles as well as for asymmetric transverse momentum configurations. In the
second case the NLO contributions vanish at small relative azimuthal angles
and/or large jet transverse-momentum disbalance due to simple kinematical
constraints. There are no such limitations for the $k_t$-factorization
approach. All this makes the two approaches rather complementary. The role of
several cuts is discussed and quantified.
