  We construct irreducible modules V_{\alpha}, \alpha \in \C over W_3 algebra
with c = -2 in terms of a free bosonic field. We prove that these modules
exhaust all the irreducible modules of W_3 algebra with c = -2. Highest weights
of modules V_{\alpha}, \alpha \in \C with respect to the full (two-dimensional)
Cartan subalgebra of W_3 algebra are (\alpha(\alpha -1)/2, \alpha(\alpha
-1)(2\alpha -1)/6). They are parametrized by points (t, w) on a rational curve
w^2 - t^2 (8t + 1)/9 = 0. Irreducible modules of vertex algebra W_{1+\infty}
with c = -1 are also classified.
