Objective: Shared decision making (SDM) for cancer treatment yields positive results. However, it appears that discussing essential topics for SDM is not fully integrated into treatment decision making yet. Therefore, we aim to explore to what extent discussion of therapy options, treatment consequences, and personal priorities is preferred and perceived by (former) cancer patients. Methods: An online questionnaire was distributed by the Dutch Federation of Cancer Patient Organisations among (former) cancer patients in 2018. Results: Among 3785 (former) cancer patients, 3254 patients (86%) had discussed treatments with their health care provider (HCP) and were included for analysis. Mean age was 62.1 ± 11.5; 55% were female. Discussing the option to choose no (further) treatment was rated by 2751 (84.5%) as very important (median score 9/10—IQR 8–10). Its occurrence was perceived by 28% (N = 899), and short- and long-term treatment consequences were discussed in 81% (N = 2626) and 53% (N = 1727), respectively. An unmet wish to discuss short- and long-term consequences was reported by 22% and 26%, respectively. Less than half of the (former) cancer patients perceived that personal priorities (44%) and future plans (34%) were discussed. Conclusion: In the perception of (former) cancer patients, several essential elements for effective SDM are insufficiently discussed during cancer treatment decision making.