Methods are provided for producing flowable compositions, e.g. pastes, that set into calcium phosphate products and include a contrast agent. In the subject methods, dry reactants that include a calcium source and a phosphate source are combined with setting fluid and a water-soluble contrast agent, e.g., a water-soluble barium salt, and the combined reactants are mixed to produce the flowable composition. Also provided are the compositions themselves as well as kits for preparing the same. The subject methods and compositions produced thereby find use in a variety of applications, including the repair of hard tissue defects, e.g., bone defects.