Resumen: This work uses tools recently designed to conduct analyses and proposals around the cultural development of medium-sized cities. The Cultural and Creative Cities Monitor model, or CCCM, is first applied to the 81 cities in Spain with between 50, 000 and 100, 000 inhabitants. We also refer to the UNESCO Culture/2030 Indicators, specifically indicator 8 (Cultural companies), to in-vestigate whether cultural dynamism is related to business vitality in those cities. Our observation of the 29 CCCM indicators and the C3 index, which synthesizes cultural performance, is explained, and these data are complemented with cultural business data (on assets, benefits, and jobs) from a sample of 13, 204 firms. The C3 index values reveal significant differences in the cultural and creative performance of the selected cities according to their location (metropolitan or non-metropolitan) and their administrative rank. Moreover, when comparing the C3 index with the indicators on business activity, evidence indicates a clear positive relationship between cultural dynamism and firm vitality. These results support the contribution of culture to the sustainable development of me-dium-sized Spanish cities and further establish the suitability of the tools used to assist cities in designing appropriate cultural policies. Idioma: Inglés DOI: 10.3390/su13137325 Año: 2021 Publicado en: Sustainability (Switzerland) 13, 13 (2021), 13137325 [29 pp] ISSN: 2071-1050 Factor impacto JCR: 3.889 (2021) Categ. JCR: ENVIRONMENTAL STUDIES rank: 57 / 128 = 0.445 (2021) - Q2 - T2 Categ. JCR: ENVIRONMENTAL SCIENCES rank: 133 / 279 = 0.477 (2021) - Q2 - T2 Categ. JCR: GREEN & SUSTAINABLE SCIENCE & TECHNOLOGY rank: 35 / 47 = 0.745 (2021) - Q3 - T3 Categ. JCR: GREEN & SUSTAINABLE SCIENCE & TECHNOLOGY rank: 7 / 9 = 0.778 (2021) - Q4 - T3 Factor impacto CITESCORE: 5.0 - Social Sciences (Q1) - Engineering (Q1) - Energy (Q2) - Environmental Science (Q2)