Radiological contamination of agricultural landscapes in the Ukrainian Polissia following the Chornobyl accident remains a long-term driver of spatially uneven ecological and food-security risks, despite a general reduction in average dose rates observed over the past decades. The issue has gained renewed relevance under war-related pressures, when land-use regimes are disrupted, monitoring infrastructure is damaged or inaccessible, and decision-makers require rapid spatial assessments without continuous field measurements. In this context, spatial planning emerges as a critical component of crisis environmental management, enabling the integration of environmental, logistical and social constraints into land-use prioritization. This study aims to evaluate the potential of spatial planning of radiologically contaminated lands as a decision-support instrument in crisis environmental management, by integrating open geospatial data, dose estimates, landscape vulnerability parameters, and indicators of anthropogenic pressure. The methodological framework was developed and tested in 2024–2025 at the Institute of Agroecology and Environmental Management (NAAS, Kyiv). The approach combines open-access radiological maps of 137Cs, population dose estimates, and land-cover information with Shuttle Radar Topography Mission elevation data and ESA WorldCover satellite products. All inputs were aggregated into a composite Radioecological Criticality Index (RECI), designed to prioritize territories at regional, oblast, and local scales. A pilot assessment was conducted north of Rozsokhivske (Zhytomyr region), with subsequent scaling to oblast-level and regional-level cartography across the broader Polissia. The results demonstrate that the majority of analyzed territories currently fall into low-critical or moderately critical classes, reflecting long-term radioactive decay, land-use shifts, and attenuation processes in soils. Nevertheless, stable clusters of high and very high criticality persist, particularly in river floodplains, poorly drained forest complexes and micro-depressions where surface runoff accumulates. These «criticality nodes» are strongly associated with elevated 137Cs levels, hydromorphic soils, and intensified biological uptake, which sustain prolonged radionuclide circulation in the soil–plant system. A comparison with existing Ukrainian radioecological maps indicates spatial compatibility in identifying high-risk zones, while the RECI-based approach provides finer territorial differentiation due to its broader parameter base, which includes landscape morphology, hydrological distance, exploitation intensity, and population dose as integral risk indicators. Importantly, the method allows risk-oriented zoning and scenario-based land-use planning without the need for new field sampling, making it practical under wartime constraints. The research confirms that RECI can serve as a functional planning tool for crisis environmental management, particularly for prioritizing remediation actions, restricting agricultural production in high-risk areas, limiting forest biomass exploitation, supporting food-safety monitoring, and developing recovery strategies for degraded agroecosystems. The resulting spatial products can inform regional policy, sustainable food-security planning, and long-term rehabilitation of territories affected simultaneously by chronic radiological stress and wartime disturbance.