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By proposing a literature review on voluntary disclosure, this article illustrates the lack of consistence in the definition of the concept. We suggest a definition of the « voluntary » feature based on objective attributes of this information : contents, sequence and vector. Although these publications are justified by the recognized limits of standardized accounting information, both managers’ opportunism and disclosure contingency challenge the validity of the voluntarily disclosed items. We propose a synthesis of works on this debate. At last, on the basis of objective considerations, restating from data-processing criteria of qualification, we underline all that keeps away voluntary information from the statute of usable information. From these reports, possible future research directions are proposed.