Multi-reference configuration interaction (MRD-CI) calculations are required to compute the vertical electronic spectrum of HC7H, because two leading configurations resulting from the excitations 2pi(u) --> 2pi(g) (HOMO-SOMO) and 2pi(g) --> 3pi(u) (SOMO-LUMO) are almost equally important in the description of the states 1(3)Sigma(u)(-) and 2(3)Sigma(u)(-). The electronic absorption spectrum is dominated by the dipole-allowed transitions to these two states from X(3)Sigma(g)(-). The lower 1(3)Sigma(u)(-) is computed at 2.55 eV in reasonable agreement with experimental work of 505 nm (2.46 eV), whereas the upper 2(3)Sigma(u)(-) is predicted close to 6.6 eV. (C) 2002 Published by Elsevier Science B.V.