The theory of angle-domain common-image gathers (ADCIGs) is extended to migrations performed in generalized 2D coordinate systems.  I develop an expression linking the definition of reflection opening angle to differential traveltime operators and spatially varying weights derived from the non-Cartesian geometry.  I demonstrate that generalized coordinate ADCIGs can be calculated directly using Radon-based offset-to-angle approaches for coordinate systems behaving locally isotropic.  The canonical examples of tilted Cartesian, polar, and elliptic coordinates are used to illustrate the ADCIG theory.  I  compare analytically and numerically generated image volumes for a set of elliptically shaped reflectors.  Experiments with a synthetic data set illustrate that relative to conventional Cartesian image volumes elliptic-coordinate ADCIGs better resolve the reflection opening angles of steeply dipping structure, due to improved large-angle propagation and enhanced sensitivity to steep structural dips afforded by coordinate system transformations.  Results from this chapter have been accepted for publication as \cite{ShraggeRADCIG}. 	
