Andisheh Mahdavi (UVIC) X-ray and Weak Gravitational Lensing Masses in the Canadian Cluster Comparison Project -------------------------------------------------------------------------------------------------------------------- Accurate galaxy cluster masses are important for progress in measuring cosmological parameters and testing theories of structure formation. We can evaluate the robustness of our masses by comparing measurements obtained using different methods. In the Canadian Cluster Comparison Project, we measure X-ray and weak gravitational lensing masses for a sample 50 clusters of galaxies observed with the CFHT, as well as the orbiting Chandra and XMM-Newton telescopes. We find that relaxed clusters of galaxies have consistent X-ray and weak lensing masses, while non-relaxed ones show a significant bias towards lower X-ray masses. We also find that the most robust and reliable predictor of the dynamical state of the cluster is also a rather inexpensive and efficient one---the distance between the brightest cluster galaxy and the X-ray surface brightness peak. Clusters with a BCG offset of less than 10 kpc (or 0.01 r500) are exceptionally well-behaved structurally and are likely ideal targets for modeling with equilibrium methods (such as hydrostatic or Jeans analysis).