One of the following usually differentiates hysterical symptoms from hypochondriacal symptoms -
Symptoms do not normally reflect understandable physiological or pathological mechanism
Physical symptoms are prominent which are not explained by organic factors
Personality traits are significant
Symptoms run a chronic course
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.