Cross-selling consists in building fundamental relationships with clients via current or mortgage credit accounts, and in the subsequent selling of new financial products. Given the powerful impact of cross-selling on the banks' financial performance, its application in marketing practice is increasingly common. The cross-selling strategy is currently pursued by the largest and most profitable global banks, such as Citigroup, Wells Fargo, Bank of America, Barclays, HSBC, UBS, and Fleet Boston. The highly successful Wells Fargo Bank managed to sell each of its clients approximately 4 financial products (nevertheless, the long-term goal of the bank is to achieve an average level of 8 products per client).

The bankers' attention to the benefits resulting from cross-selling was attracted by the findings of studies conducted over the last decade. These findings show that the cost of attracting a new client may be as much as 5 times higher than the cost of encouraging an existing client to take advantage of additional financial services. Furthermore, banks tied by strong and multidimensional client-relations have an information-based advantage over the banks that aim to conclude single transactions (the processing of credit applications is easier along with the monitoring of the borrower's financial standing during the course of the crediting period). By selling additional products to existing clients, the bank not only raises the profitability of the relationship but at the same time establishes a network of ties that will be difficult to sever in the future.

The interesting thing is that clients (in particular, retailers and small businesses) are also interested in strengthening their ties with the bank (the findings of opinion polls conducted in the US by Bank Administration Institute and Cambridge Group in 2000 indicated that there is a 94% likelihood that a client holding a check account at a given bank will also make use of other products). This happens because clients are likely to gain a lot of benefits through intensive co-operation with a single provider of financial services (first of all, they save time and money). When applying for credit, they do not have to prepare full documentation on every occasion regarding their financial situation, do not need to wait for a long time for their application to be processed (credit history and history of operations conducted in the current account substantially simplify and shorten all procedures) and do not need to learn new procedures. Owing to easier access to credit lines and higher credit limits they are able to manage their finances in a flexible manner. The comprehensive service is also very important to clients, as well as the possibility to obtain special prices (banks usually offer their own reliable clients more advantageous terms).

Although in Poland the issue of cross-selling has not been so far described in detail in the banking and marketing publications, empirical research (presented in the paper) shows that some Polish banks are already very successful at selling additional products to the existing client base.