This review paper by John R. Best and Patricia H. Miller examines the theoretical and methodological issues in constructing a developmental perspective on executive function (EF) in childhood and adolescence. Unlike most reviews that focus on preschoolers, this paper focuses on studies that include a wide age range, from early childhood to adolescence. It outlines the development of three foundational components of EF—inhibition, working memory (WM), and shifting—and discusses the cognitive and neurophysiological assessments that show significant strengthening of EF throughout these stages. The paper relates these findings to longstanding issues in development, such as sequences, trajectories, and processes, and suggests future research needed to build a comprehensive developmental framework. The authors address the limitations of narrow age ranges and the lack of studies examining developmental sequences and mechanisms. They highlight the challenge of defining EF as a unitary construct or a set of independent components, using Miyake et al.'s "unity and diversity" framework to integrate these perspectives. They review studies that support this framework, showing that EF components are both interrelated and distinct, with varying degrees of unity and independence across different age groups. The paper also discusses the methodological challenges in studying EF, such as task imparity and the use of complex tasks that tap into multiple EFs. It emphasizes the importance of using a wide age range and uniform tasks to avoid ceiling effects and ensure valid comparisons. The foundational EFs—inhibition, WM, and shifting—are examined in detail. Inhibition is considered foundational, with rapid improvements in early childhood on complex response inhibition tasks. WM development is characterized by a protracted course, with continued refinement through adolescence, especially for tasks requiring the maintenance and manipulation of multiple items. Shifting, the ability to switch between mental states or tasks, is also discussed, highlighting the need for inhibition and WM processes. Neuroscience evidence supports the developmental changes in neural activity underlying these EFs, showing increases in localized and efficient activation in specific prefrontal regions. The paper concludes by suggesting that future research should focus on the developmental trajectory, sequences, and mechanisms of EF, particularly in the transition from preschool to adolescence.This review paper by John R. Best and Patricia H. Miller examines the theoretical and methodological issues in constructing a developmental perspective on executive function (EF) in childhood and adolescence. Unlike most reviews that focus on preschoolers, this paper focuses on studies that include a wide age range, from early childhood to adolescence. It outlines the development of three foundational components of EF—inhibition, working memory (WM), and shifting—and discusses the cognitive and neurophysiological assessments that show significant strengthening of EF throughout these stages. The paper relates these findings to longstanding issues in development, such as sequences, trajectories, and processes, and suggests future research needed to build a comprehensive developmental framework. The authors address the limitations of narrow age ranges and the lack of studies examining developmental sequences and mechanisms. They highlight the challenge of defining EF as a unitary construct or a set of independent components, using Miyake et al.'s "unity and diversity" framework to integrate these perspectives. They review studies that support this framework, showing that EF components are both interrelated and distinct, with varying degrees of unity and independence across different age groups. The paper also discusses the methodological challenges in studying EF, such as task imparity and the use of complex tasks that tap into multiple EFs. It emphasizes the importance of using a wide age range and uniform tasks to avoid ceiling effects and ensure valid comparisons. The foundational EFs—inhibition, WM, and shifting—are examined in detail. Inhibition is considered foundational, with rapid improvements in early childhood on complex response inhibition tasks. WM development is characterized by a protracted course, with continued refinement through adolescence, especially for tasks requiring the maintenance and manipulation of multiple items. Shifting, the ability to switch between mental states or tasks, is also discussed, highlighting the need for inhibition and WM processes. Neuroscience evidence supports the developmental changes in neural activity underlying these EFs, showing increases in localized and efficient activation in specific prefrontal regions. The paper concludes by suggesting that future research should focus on the developmental trajectory, sequences, and mechanisms of EF, particularly in the transition from preschool to adolescence.