<p>With the growth of mobile data consumption, mobile network operators offer customers various data plans. Among them, operators widely adopt two data plans. One is the <i>“deceleration data plan”</i> that charges a monthly subscription fee given a certain data cap but lowers the network speed if consumers’ data usage exceeds the cap. The other is the <i>“charging data plan”</i> that allows customers to keep high-speed data usage for an extra charge if the cap is exceeded. Due to the prevalence of these two data plans, we develop a stylized model to study the data plan selection problem for a profit-maximizing or welfare-maximizing mobile network operator and examine the impacts of different data plans on pricing decisions, profit, and consumer surplus. We find that if the data cap is sufficiently low (high), the optimal price of the deceleration data plan is higher (lower) than that of the charging data plan for a profit-maximizing operator. For a welfare-maximizing operator, however, the price of the deceleration data plan is always higher than that of the charging data plan. Moreover, we show that a profit-maximizing operator would adopt the deceleration data plan if both the customers’ value of data and the cap are sufficiently low or high, and they would choose the charging data plan otherwise. However, a welfare-maximizing operator might adopt the charging data plan if the data value is sufficiently high. Specifically, if both the value of the data and the cap are sufficiently low, the operator will choose the deceleration data plan, and otherwise adopt the charging data plan. We also confirm that the consumer surplus of the charging data plan is always higher than that of the deceleration data plan. Finally, we extend our basic model to the cases where the data cap is endogenous, consumer data usage is normally distributed, and different consumer groups have different data usage ranges, respectively, and we show that our main results still hold.</p>