An analysis of the distribution of the squared S-matrix elements and of the nearest neighbour distribution of the eigenphases of the S-matrix has been performed for the two reactive atom-diatom collisions N(D-2) + H-2 --> NH + H and F(P-2) + D-2 --> FD + D at fixed total energy. The first is an indirect reaction which involves a long-lived intermediate complex, whereas the second is a direct reaction with a short-lived intermediate complex. Quantum chaos has been found for the N + H-2 reaction whereas the F + D-2 reaction follows a non-chaotic regime.