Consumers often make choices using incomplete information. When an information set presented in a choice setting is incomplete, consumers may make inference about the existence of missing attributes. Such inferences create what we call `phantom attributes,' which influence choice but are latent artifacts of the decision process. Phantom attributes increase the original set of attributes and, as such, are distinct from a mediation processes which consolidate attributes. In three studies, we demonstrate that phantom attributes can meaningfully impact decisions as they interact with price, brand, and other complex or perceptual attributes. We provide a practical approach to measuring phantom attributes and determining their impact on choice. This approach has practical implications for product positioning and pricing, especially in contexts with limited information like digital advertising, package design, and item listings in digital marketplaces. Phantom attributes generalize price-quality effects and can serve as a mechanism for brand-based contrast effects.