Objectives: The purpose of the present study was to compare deaf and hearing students' writing and describe the themes, based on Halliday & Matthiessen's Systemic Functional Grammar. Method: The population was selected among deaf and hearing students in the fifth grade primary school in Tehran. Forty male students were recruited through available sampling and the writing sample was elicited. Then they were analyzed by the independent t test. Results: Results showed a significant difference between deaf and hearing students' writing in terms of applying various types of themes. Conclusion: The writing quality in deaf students in applying marked and complex themes is completely lower than their hearing peers'.