We have carried out density matrix renormalization group calculations on the T-1 state of linear polyenes applying the Pariser-Parr-Pople (PPP) Model. The geometry optimization for the polyene oligomers C2nH2n+2 (n=4,5,6,...,15) shows that the S-0 to T-1 excitation region is composed of a soliton-antisoliton pair located symmetrically away from the center of the chain and leads to single- and double-bond interconversions in between. The distance between the soliton and antisoliton centers in T-1 state changes with the length of the chain, contradictory to earlier conclusions obtained with PPP-SDCI or ab initio SCI methods. The inconsistency most possibly comes from the insufficient consideration of the electron correlations in small-scale CI methods. (C) 2004 American Institute of Physics.