One of the following usually differentiates hysterical symptoms from hypochondriacal symptoms -
The preoccupation in hypochondriasis is based on a misinterpretation of physical symptom in the presence of normal body function. For example, an occasional change in heart rate will lead a person with hypochondriasis to fear of severe heart disease.
On the other hand, hysterical symptoms are not due to misinterpretation of physiological response.