The subject of this paper is self-organized solitary current filaments being observed experimentally in a planar dc gas-discharge system with high-ohmic barrier. We report on the dynamical behavior of these objects which we refer to as dissipative solitons. An application of stochastic data analysis methods enables the separation of intrinsic dynamics from stochastic contributions. Using the externally applied voltage as control parameter, we observe a drift bifurcation that is accompanied by a change of shape of the bifurcating dissipative soliton. In order to interpret the experimental finding, a theoretical model in form of a three-component reaction-diffusion system is considered, allowing for a qualitative understanding of the obtained results. We discuss an analytical expression for the velocity of the dissipative soliton as a function of an appropriate control parameter and demonstrate that the change of the shape can induce the drift bifurcation. This analytical finding is supported by numerical simulations of the model equations. (C) 2004 Elsevier B.V. All rights reserved.