The chemical composition of propolis is diverse and depends on the geographical and botanical origin, i.e., climate factors, plant resources, place of origin, and time in which it was collected by the bees [5,17]. Honey bees collect plant material for propolis production during the warmest hours of sunny days because of the malleability and softness of the resins that are an essential component of propolis. Therefore, in temperate regions, propolis production takes place from late summer until autumn, whereas in tropical regions, honey bees can collect plant material throughout the entire year [6]. The specificity of the local flora is the main factor that determines the chemical composition of propolis and, subsequently, its biological and pharmacological properties [5]. Based on the origin of the propolis plant components, it has been classified into seven major types: 1. poplar (Europe, China, New Zealand, North America, and Southern South America); 2. birch (Russia); 3. Mediterranean (Sicily, Greece, Crete, and Malta); 4. green (South-eastern Brazil); 5. red (Cuba, North-eastern Brazil, and Southeast Mexico); 6. Clusia (Venezuela and Cuba); and 7. Pacific (Okinawa, Taiwan, Indonesia, and Hawaii) [6,18]. Poplar types propolis originate mainly from the bud exudates of Populus spp. and mainly contain flavonoids (flavones and flavanones), phenolic acids (cinnamic acid), and their esters. Birch propolis originates from Betula verrucosa Ehrh. and also contains flavones and flavonols but is different from poplar propolis. In the Mediterranean region, honey bees mainly collect the resin of Cupressus sempervirens, therefore, Mediterranean propolis is rich in diterpenes. Green propolis contains derivatives of phenylpropanoides and diterpenes, chlorophyll and small amounts of flavonoids collected by bees from young tissues and nonexpanded leaves of Baccharis dracunculifolia. Contrary to green propolis, its red type is rich in numerous flavonoids (pinobanksin, quercetin, pinocembrin, daidzein), the source of which are resins of Dalbergia ecastaphyllum. The Clusia type of propolis contains benzophenones derivatives and originates from the resin of flowers of Clusia sp. Other examples of tropical propolis is Pacific propolis characterized by content of C-prenylflavanones [3,18,19]. The chemical composition and biological activities of propolis extracts depend on the type of solvent used for the extraction. The most commonly used solvent for the extraction of propolis is ethanol (particularly at a concentration of 70–75%) [18,20]. Propolis extracts are also obtained by extraction with solvents such as water, ethyl ether, methanol, hexane, chloroform, glycolic and glyceric solution, and seed oil [18,21]. In fact, in pharmaceutical and health care products, propolis is added in the form of ethanolic and aqueous extracts [21]. The available methods of analyzing the chemical composition of propolis and plant materials included in propolis as well as standardization and quality control methods for industrial applications have been described by Bankova and colleagues [22]. In general, propolis is composed of 50–60% of resins and balms, 30–40% of waxes and fatty acids, 5–10% of essential and aromatic oils, 5–10% of pollen, and about 5% of other substances, such as amino acids, vitamins, macro-, and microelements [5,8,18,23]. According to the literature data, more than 300 compounds have been identified in propolis samples of different geographical origins [15,18,20,23]. The major chemical groups found in propolis are flavonoids, aliphatic and aromatic acids, phenolic esters, fatty acids, alcohols, terpenes, β-steroids, alkaloids that include, but are not limited to chrysin, pinocembrin, apigenin, galangin, kaempferol, quercetin, cinnamic acid, o-coumaric acid, p-coumaric acid, caffeic acid (CA), and caffeic acid phenylethyl ester (CAPE) [3,5,15,24]. Flavonoids are the main substances responsible for the pharmacological properties of propolis, while terpenoids are additionally responsible for the odor of propolis [3]. The biological activities of propolis are the results of the interaction between various compounds. Analysis of the activity of each compound alone allows exploration of the molecular mechanisms underlying the pharmacological properties of propolis [23]. Table 1 summarizes the results of recent in vitro and in vivo studies on the influence of propolis and its active compounds on the processes related to cancer development.