An investigation was carried out on the surface morphological features of two types of mesoporous sorbents derived from fine hydrated lime powder, termed H-CaO and C-CaO. Specifically, the surface fractal dimensions, d(SF)’s, of the sorbents obtained at various temperatures of calcination have been determined from their respective adsorption-desorption isotherms of nitrogen measured at 77 K, by a recently proposed thermodynamic method of analysis. A definite trend in the variation of d(SF) with the temperature of calcination has been discerned for both sorbents. Moreover, the d(SF) for each sorbent attained a maximum at 1273 K. The results of the present work may facilitate our understanding of various phenomena occurring on the irregular interfaces of heterogeneous systems at elevated temperatures.