The effect of bed height on CO 2 capture was investigated by carbonation/regeneration cyclic operations using a bubbling fluidized bed reactor. We used a potassium-based solid sorbent, SorbKX35T5 which was manufactured by the Korea Electric Power Research Institute. The sorbent consists of 35% K 2 CO 3 for absorption and 65% supporters for mechanical strength. We used a fluidized bed reactor with an inner diameter of 0.05 m and a height of 0.8 m which was made of quartz and placed inside of a furnace. The operating temperatures were fixed at 70 o C and 150 o C for carbonation and regeneration, respectively. The carbonation/regeneration cyclic operations were performed three times at four different L/D (length vs diameter) ratios such as one, two, three, and four. The amount of CO 2 captured was the most when L/D ratio was one, while the period of maintaining 100% CO 2 removal was the longest as 6 minutes when L/D ratio was three. At each cycle, CO 2 sorption capacity (g CO 2 /g sorbent) was decreased as L/D ratio was increased. The results obtained in this study can be applied to design and operate a large scale CO 2 capture process composed of two fluidized bed reactors.