Three absorption systems with origins at 354, 497, and 528 nm were detected after mass-selected deposition of H2C6O+ in a 6 K neon matrix. The ions were formed by the reaction of C2O with HC4H+ in a mixture of C3O2 and diacetylene in a hot cathode source, or by dissociative ionization of tetrabromocyclohexadienone. The 497 and 354 nm systems are assigned to the 1(2)A" <- X(2)A" and 2(2)A" <- X(2)A" electronic transitions of B+, (2-ethynylcycloallyl)methanone cation, and the 528 nm absorption to the 1(2)A(2) <- (XB1)-B-2 transition of F+, 2-ethynylbut-3-yn-1-enone-1-ylide, on the basis of calculated excitation energies with CASPT2.