ISA Brown hens aged 24–36 weeks and hens aged 56–68 weeks were used to study the influence of limestone particle size and the animal’s age on laying performance and egg quality. Two diets were used: a diet containing calcium carbonate in fine limestone particles (LF), and a diet containing calcium carbonate in coarse limestone particles (LC). Lower egg production in hens aged 56–68 weeks was compensated in part by higher egg weight. In younger and older hens, feeding the LC diet increased hen-day egg production (P < 0.001), shell weight by 0.2 and 0.2 g (P < 0.001), shell thickness by 4 and 8 µm (P < 0.001), shell Ca content by 2 and 2 mg/g DM (P = 0.003), albumen height by 0.2 and 0.3 mm (P = 0.003), and Haugh units by 0.8 and 0.2 (P = 0.014), respectively. It can be concluded that LC should be considered rather than LF when formulating diets for laying hens both in the early and the late phase of production.