Dandelions have been reported to have medicinal properties and bioactive components that impact human health. However, the precise biological properties of dandelions and the parts of the plants possessing bioactive components remain uncertain. In this study, we evaluated 3 different types of dandelions based on their cultivation origin (Songpa, Uiryung, and native Uiryung types) as well as their 4 different plant parts (leaf, flower, root, skin). Each sample was extracted with $80\%$ methanol and then compared for the biological activities (anti-oxidative, immune cell proliferative and tumor cell growth inhibitory activities). All 3 types of dandelions possessed a degree of biological functions including the hydroxyl radical scavenger activity, immune cell proliferative activity and tumor cell growth inhibitory activity. However, there was no significant difference in these activities between the 3 dandelion types. Leaves of all three dandelion types showed the highest levels of all biological activities. To a lesser degree, the flower and root parts displayed biological activities. In the skin parts, anti-oxidative activity was also detected only at higher doses of dandelion extracts. Heating the dandelion leaf extract did not affect the biological activity, suggesting a heat-stable nature of the biological compounds. Taken together, these collective data suggest that dandelions, in particular their leaves, possess a high concentration of heat-resistant biological compounds, which are responsible for anti-oxidative, immune cell proliferative and tumor cell growth-inhibitory activities.