This article explores how firms can foster positive consumer inferences by communicating their new product development (NPD) openness. In particular, it analyzes inferences about a firm's customer orientation, ability to develop high-quality products and innovativeness. Previous research has focused on examining inferences derived from cues about consumer contributions to the external design of products. This article extends current knowledge (i) by analyzing inferential processes when customer participation goes beyond external product design and affects functionality and (ii) by considering other forms of openness, namely expert contributions to NPD. The results of two experiments show that, in general, customer participation in NPD effectively triggers customer orientation inferences, while expert participation leads to inferences about a firm's ability to develop high-quality products only in specific settings. Finally, counter to previous research, communicating external participation does not seem to be an effective cue to infer innovativeness for functional product contributions.