The article presents the role of electronic markets in contemporary economy and, especially, their impact on relations between companies and their suppliers, as well as end-users of sold products. One can distinguish between marketplace and marketspace, where electronic transactions are concluded. While traditional marketplaces have a physical location, Internet-base markets have no physical presence – it is a virtual marketplace. The new electronic marketspace has many alternative virtual locations where an organisation needs to position itself to communicate and to sell to customers. There are three important e-markets that both sell and buy to each other: businesses, consumers and governments; B2B, B2C, B2G. Three key online locations for performing e-commerce transactions with customers can be identified: seller-controlled sites; buyer-controlled sites and neutral sites. Such so-called organised markets as exchanges, auctions, tenders and fairs can function both in marketplace and in marketspace. Companies operating on electronic markets are looking for major benefits to improve their competitive position under conditions of globalisation and deregulation of economic activities. They should take advantage of opportunities and avoid threats connected with e-transactions.