Mobile phones were initially meant only for communication. With the development of technology and appearance of smartphone handsets, we have become witnesses to the rapid development and modification of the concept and purpose of the phone. Given the increasing availability of smartphone, mobile application development is one of the fastest growing aspects of ICT. The theme of this paper is development of applictions for iPhone and Android platforms, and it involves the creation of conceptual design, market development and design of the design and placement of applications on the market. Applications have different functions and the user selects them depending on their interests and needs, for business, entertainment, sports, news, travel, GPS navigation, social networking, etc. This means that the application is a place for fun, work or simply a place where the user comes for information. Apple, as a leading manufacturer of smartphones, with first version of its mobile phone was able to reverse all the previous market. Presented user interface in the first place puts the user, and a powerful hardware platform capable of performing complex applications. Because of this, this paper traces the development of Croatian applications, travel guides for iPhone on the Croatian territory. It puts the emphasis on applications design, and the impact of design on the usage of the same. People are visual creatures, and at first glance unconsciously give importance on the appearance, and on the design of user interface depends on whether they will spend time watching it or not. Steve Jobs said: „Design is not just what it looks like and feels like. Design is how it works.“