If a person is not afraid of non-existance then if he is afaid of death he is actually afraid of the possible pain involved ; does this seem reasonable?
You are reasoning along the lines of Epicurean philosophers, who argued that death is non-existence and therefore should not matter to us. (See a nice discussion of this in Havi Carel's recent book "Illness.") You are perhaps wondering how to interpret a lingering fear of death, and suggesting that such a fear may be rational if it is fear of the possible pain involved in dying. It's also possible that a lingering fear of death is not rational.