Introduction: Standardization of data items collected in paediatric clinical trials is an important but challenging issue. The CDISC data standards are well understood by the pharmaceutical industry but lack the implementation of some paediatric-specific concepts. When a paediatric concept is absent within CDISC standards, pharmaceutical companies and research institutions take multiple approaches in the collection of paediatric data, leading to different implementations of standards and potentially limited utility for reuse. Objective: To overcome these challenges, the conect4children consortium has developed a cross-cutting paediatric data dictionary (CCPDD). Methods: The dictionary was built over three phases: scoping (including a survey sent out to ten industrial and 34 academic partners to gauge interest), creation of a longlist and consensus building for the final set of terms. The dictionary was finalized during a workshop with attendees from academia, hospitals, industry and CDISC. The attendees held detailed discussions on each data item and participated in the final vote on the inclusion of the item in the CCPDD. Results: Nine industrial and all 34 academic partners responded to the survey, which showed overall interest in the development of the CCPDD. Following the final vote on 27 data items, three were rejected, six were deferred to the next version and a final opinion was sought from CDISC. The first version of the CCPDD with 25 data items was released in August 2019. Discussion and Conclusion: The continued use of the dictionary has the potential to ensure the collection of standardized data that is interoperable and can later be pooled and reused for other applications. The dictionary is already being used for case report form creation in three clinical trials. The CCPDD will also serve as one of the inputs to the Paediatric User Guide, which is being developed by CDISC.