OverviewThis dataset contains anonymised responses from 3,395 children and adolescents (ages 7–17) who participated in the Aire Limpio environmental health programme in the Region of Murcia (Spain). Data were collected between 4 March and 4 April 2022 via an online school-based questionnaire.The dataset operationalises the Nature Connection and Experience Index (NCEI), combining: • Connection to Nature (CN) items adapted from the Children’s Connection to Nature Index (CNI). • Nature Experiences (NE) indicators (frequency/duration/type of everyday nature contact). Lead author and primary responsible person (Contact person):The lead author conceived the study, developed the conceptual framework, and created the electronic tool used for data collection and management. He coordinated all processes related to the dataset deposit, including supervision, quality control, permissions, and data storage management.He was also fully responsible for data acquisition through the Aire Limpio programme, ensuring standardized and high-quality data collection. In addition, he organised the dataset structure, oversaw data distribution, and contributed extensively to the preparation and final curation of the dataset for publication and reuse. Contributors (data preparation):Francisco Díaz Martínez and Laura T Cabrera Rivera provided substantial technical support in data cleaning, structuring, and preparation. They contributed to harmonising data formats, verifying internal consistency, and ensuring the dataset met quality and documentation standards, under the coordination of the lead author.