Confinement effects on the electric properties of model system are investigated. The system under consideration is 1-cyanoethyne molecule surrounded by helium atoms arranged in the shape of armchair nanotube. Decreasing the diameter of the helium nanotube corresponds to the simulation of the confinement effects on the enclosed system. The decomposition of the interaction energy and interaction-induced electric properties reveals that dispersion terms plays an important role in the interaction between subsystems. It is observed that the absolute values of dipole moment and first-order hyperpolarizability decrease as a function of the tube radius. (C) 2007 Elsevier B.V. All rights reserved.