In mobile computing, there is variety of approaches to develop applications. One challenge is the diversity of mobile devices in the market and targeting more than one mobile device to develop applications. One approach to handle this is traditional, in which for every device there is a project carried out to develop application. Another method is the cross-platform application development which has been introduced in recent years. The purpose of this thesis is to explore if existing cross-platform frameworks can aid startup companies to develop cross-platform mobile apps. The research questions are 1) How can cross-platform frameworks be a viable approach for start-up companies in this respect? 2) What challenges and benefits do cross-platform approaches bring to developers? In order to answer the research questions, respondents from five small-sized and two large companies developing mobile apps are being interviewed. The results shows that cross-platform frameworks are good tools when developing mobile apps for multiple platforms, but are applicable to different degrees depending on the actual case. Challenges and benefits identified by the respondents mainly touched upon decreasing development time, and less coding effort, but also the uniqueness of Apple and Android products and difficulties in making developers switch to new languages.