Let q be a prime power, \(\mathbb {F}_q\) the finite field with q elements, and \(f \in \mathbb {F}_q[t]\) a monic polynomial. Write \(\Omega (f)\) for the number of monic irreducible factors of f, counted with multiplicity. We obtain asymptotic estimates for the distribution of \(z^{\Omega (f)}\) by developing a function-field analogue of the Selberg–Delange method, then use it to count monic polynomials of a given degree and a given value of \(\Omega \) . This approach sharpens and extends earlier results in the literature concerning this function.