Radioactive iodine therapy is the most common treatment for Graves' disease and toxic multi-nodular goiter in adult Aim: to evaluate the effect of nursing instructions on life style of thyroid disorders patients receiving radioactive iodine therapy (RAI). Patients and methods: the study was conducted in Nuclear Medicine department of Assiut university hospital and South Egypt Cancer Institute. A convenience sample (60) adult thyroid disorder patients from both sex, who were admitted in the Nuclear Medicine department for RAI therapy. Tools Patient interview Questionnaire, patient's life style questionnaire: (Walker, K. Sechirst, N. Pender., 1995) and designed nursing instructions booklet Results: the study group patient achieved a satisfactory level of knowledge after application of the nursing instructions (86.7%). There was a highly statistically significant difference between the study group pre & post implementation of the nursing instructions (P.v 0.001). Conclusion: there was an improvement in knowledge level after implementation of the nursing instructions in the study group, 86.7%, there was a highly statistically significant difference between the study group patients pre and post application of nursing instructions. An improvement of life style in the study group after implementation of nursing instructions. Recommendations: Equip the nuclear unit with: nursing instructions booklet covering instructions about improving life style of patients receiving RAI therapy.