We report an ab initio study of the static electric (hyper)polarizability of diacetylene and its dependence on the single (C-C) and triple (C C) bond length. At the CCSD(T) level of theory we find for the mean dipole polarizability and its derivatives α=49.10e 2 a 0 2 E h - 1 ,( α/ R C - C ) e =-4.41 and ( α/ R C C ) e =34.57e 2 a 0 E h - 1 . For the anisotropy Δα=54.45e 2 a 0 2 E h - 1 , ( Δα/ R C - C ) e =-20.42 and ( Δα/ R C C ) e =64.56e 2 a 0 E h - 1 . The dependence of the mean hyperpolarizability on R C - C and R C C around the equilibrium is quite distinct. Varying the single bond by ΔR/a 0 around the equilibrium entails changes of[γ(R C - C )-γ(R e )]/e 4 a 0 4 E h - 3 =-3643ΔR-230ΔR 2 -184ΔR 3 +453ΔR 4 T he mean second hyperpolarizability increases strongly with R C = C around the equilibrium[γ(R C C )-γ(R e )]/e 4 a 0 4 E h - 3 =22259ΔR+11293ΔR 2 +2384Δ R 3 +6445ΔR 4