The effect of carbon surface area on capacity is investigated in cathodes for lithium sulfur batteries. Carbon additives help overcome the low electrical conductivity of sulfur. Cathodes were prepared at 30 wt% sulfur on different activated carbons having unloaded BET surface areas of 1200-3200 m2/g. Sulfur utilization ranged from 33% to 83% of the theoretical capacity (1672 mAh/g) with a strong correlation to the accessible pore volumes having pore widths between 1 and 5 nm. Additionally, cathodes prepared at 12.5-68 wt% on an activated carbon having unloaded BET surface area of 3200 m2/g showed excessive sulfur loading provided little additional capacity.