Introduction: Numerous quantitative studies have shown the importance of executive functions (planning, attention, inhibition, and short-term memory) for diabetes treatment compliance. Those studies also point to the paucity of data on action strategies employed by persons with diabetes. The aim of this study is to characterize the action strategies used in six situations typically encountered by persons with Type 1 diabetes (no comorbidities). Methods: This qualitative multiple-case study concerns adult patients with no comorbidities. Eighteen patients were presented with six clinical vignettes portraying emblematic situations and then interviewed. After categorization, the 108 situations were used to produce an intra-case and then an inter-case synthesis. Results: The study identified three groups of patients with three distinct strategies for dealing with a variety of situations. The first group used executive functions to adhere to pre-established patterns and avoid situations of uncertainty, while the second group was more likely to use it to adapt to the unexpected. The third group had no operational routines or habits and few rules. Unable to rely on habits, those patients had to proceed by trial-and-error, thus placing themselves in risky situations. Conclusion: Determining the type of cognitive strategies used by a given patient could be helpful in improving that patient’s self-knowledge. By including a personalized analysis of action strategies and potential alternatives, patient education programs could help patients better prepare for unexpected situations.