When Procter & Gamble is deciding whether to put its advertisements on television or elsewhere, it puts a call in to Nicosia, Cyprus. The same holds true for Nissan and dozens of other leading corporations and marketing-services agencies.

The calls are requests for help and go to Nicosia because the city is the home of Integration, a small consultancy that has gained prominence by taking on one of the biggest questions facing advertisers: how to pick the best medium for a particular marketing message.