Hemp is rich in polyunsaturated oils - both omega 6 and omega 3, in a particular good ratio. Ground flax seeds or flax oil is good for topping up omega 3 deficiency, but hemp seeds/oil are good for then maintaining a healthy ratio of omega 6/3.
Omega 3 and 6 oils are essential fatty acids (EFA), of which most people (according to nutritionists) are deficient. These EFAs are essential nutrients like various vitamins and minerals, and cannot be made by the human body - we should be consuming more of them, especially omega 3. The body uses these 'good fats' for a variety of tasks in the body, and its believed that they for example, can help weight control, despite their high calorific values.