Is it abnormal if I do not have frontal sinuses?
Some people only have one frontal sinus or none at all.  This is a normal variant and is nothing to worry about.  You are born without frontal sinuses and they develop (to a varying degree) after birth.  If you do not have one, it simply did not develop.

* Note: The information contained in these pages is for educational purposes only. It should not be construed as individualized diagnostic and treatment advice.