Product involvement plays a crucial role in consumer purchasing decisions. Consumers with varying levels of involvement assign different values to products and are influenced by distinct product attributes. This paper investigates how product line design and pricing decisions are influenced by consumer involvement, considering product quality and advertising as key drivers of purchasing behavior. The findings indicate that both single-product and multi-product strategies are viable under certain conditions, contingent on the relative advertising-quality cost coefficients and the distribution of consumers with different levels of involvement. Specifically, firms are likely to adopt a multi-product strategy when: 1) the relative cost coefficient is sufficiently low, and the proportion of low-involvement consumers is sufficiently high; 2) the relative cost coefficient is moderate; or 3) the relative cost coefficient is high, and the proportion of low-involvement consumers is substantial. Otherwise, a single-product strategy will be favored. These results offer valuable insights into optimizing product line design and pricing decisions.