Mizaj (Temperament) is one of the foremost and basic concepts of Unani medicine. Diagnosis and line of treatment of a disease are based on Mizaj of the patient and the drugs given for the treatment. Every human being has been endowed a specific Mizaj upon which structures and functions of his body are dependent. If the Mizaj of a person is changed his functions as well as structures tend to change. There are some factors responsible for alteration of the Mizaj like age, diet, weather, residence, occupation and habit. These factors play an important role in changing the Mizaj and in causing diseases in an individual. For example, the persons of Barid Mizaj (cold temperament) are generally susceptible to develop Suddah (obstruction) in the body and obesity etc. Similarly the persons of Har Mizaj (hot temperament) will be prone to hot diseases like fever etc. Therefore, for maintaining health it is necessary to find out the Mizaj of the patient, disease and the drugs given for the treatment. By the assessment of Mizaj of an individual and the changing factors we can predict about health status and the diseases for which individual is more prone to develop in future. Objective of the study was to find out the range of pulmonary functions in Healthy Young Adults of Different Mizaj. The present study is cross sectional. Total 100 healthy young adults fulfilling the criteria were enrolled in the study. Following enrolment of the volunteers, their Mizaj were assessed by two predetermined proforma that were based on objective and subjective parameters given by Eminent Unani physicians i.e. A'lamat Ajnase A'shra (ten determinants) and A'lamat Ghalbae Akhlat (signs and symptoms of dominance of Humour). In the present study, our emphasis was on Mizaj of individual and its relation with pulmonary functions, therefore, the present concordance between Mizaj and pulmonary functions in young healthy adults was evaluated. Further study on large scale is needed to determine relationship between Mizaj and pulmonary functions considering the factors responsible for change in the Mizaj.