Both trays and packings have been used in acid gas absorbers for many years. Some applications of each have been very successful, while others turned troublesome. This paper outlines some of the experiences and addresses the question in which situations one of the internal types performed better or worse than the others. Factors like fouling, presence of hydrogen, turndown, and absence of distribution issues have favored trays. Factors like low pressure drop and issues with foaming, especially with poorly-sized downcomers, have favored packing. Packing that have been successful in this service have been random packing. Structured packing have been used to a lesser extent due to their high cost, the need to go to more corrosion-resistant metallurgy, issues with performance at high flow parameters, the difficulty of inspecting tower walls in corrosive environments, and concerns about shutdown fires.