Hierarchically decomposed component-based system development reduces design complexity by supporting distribution of work and component reuse. For product line development, the variability of the components to be deployed in different products has to be represented by appropriate means. In this paper, we propose hierarchical variability modeling which allows specifying component variability integrated with the component hierarchy and locally to the components. Components can contain variation points determining where components may vary. Associated variants define how this variability can be realized in different component configurations. We present a meta model for hierarchical variability modeling to formalize the conceptual ideas. In order to obtain an implementation of the proposed approach together with tool support, we extend the existing architectural description language MontiArc with hierarchical variability modeling. We illustrate the presented approach using an example from the automotive systems domain.