Background - The objective of this study was to examine, using French registries, geographical variations in trends in the incidence of thyroid cancer among women according to tumor size, from 1983 to 2000. Method. - Trends in thyroid cancer incidence were analyzed using data collected between 1983 and 2000 by six cancer registries in the FRANCIM network, covering seven departments. Five lesion size categories were identified: less than 10 mm, 10–20 mm, 20–40 mm, greater than 40 mm, and unknown size. The analysis was performed by size for all papillary cancers in women in each department. World-standardized incidence rates were calculated, and annual percentage changes were estimated for each size category. A Poisson regression was used to compare trends observed across the six geographic regions. Results. - The six registries participating in the study recorded 2,222 papillary thyroid cancers in women between 1983 and 2000. An increase in the incidence of thyroid cancer, particularly small-sized lesions, was observed in all six registries. Geographic variations in the trends of thyroid cancer incidence across the registries were primarily driven by differences in the incidence trends of lesions smaller than 10 mm. Conclusion. - The greater geographic disparities in the trend of papillary cancer incidence among small lesions appear consistent with the hypothesis of heterogeneity in the management of thyroid diseases across the departments studied.