Planning, or the ability to simulate and execute a sequence of steps toward a goal, is integral for success in a range of activities, from cooking a meal to developing a new software program. Indeed, robust planning abilities have been found to predict success in math for children and the maintenance of independence in older adults. Due to the significant real-world impact of developing and sustaining strong planning abilities over the lifetime, bolstering these skills through training could prove highly beneficial for a host of life outcomes. However, it remains unclear whether the measurement tasks currently used to assess planning abilities are addressing a consistent and cohesive cognitive construct. Although planning researchers have identified tasks they believe tap planning skills, these tasks have not been subjected to individual differences testing to assess the relationship between them. Therefore, the present study investigated the associations between three tasks used to measure planning in psychology and adjacent fields (the Tower of London task, the Zoo Map test, and the Traveling Salesperson Problems) in two samples; an original study and in a pre-registered replication. Contrary to their characterization as tasks designed to measure a skill under a common semantic label, the correlations between planning tasks found in this study were negligible and unstable between samples. The lack of reliable associations between tasks indicates that they are very likely not measuring the same underlying skill, and thus, should be viewed with caution when used to measure planning individually.