The importance of metadata has been broadly referred in the last years, mainly in the field of data warehousing and decision support systems. Contemporarily, in the adjacent field of data quality, several approaches and tools have been set out for the purpose of data profiling and cleaning. However, little effort has been made in order to formally specify metrics and techniques for data quality in a structured way. As a matter of fact, little relevance has been assigned to metadata regarding data quality and data cleaning issues. This paper aims at filling this gap, proposing a conceptual metamodel for data quality and cleaning, both applicable to operational and data warehousing contexts. The presented metadata model is integrated with OMG’s CWM, offering a possible extension of this standard toward data quality. .