Software requirements specification is an important foundation of the software development process. It documents the requirements, expectations, and restrictions for a system to be developed. It should describe what the produced system will offer in detail and unambiguously. It should also provide a realistic basis for estimating product costs, risks, and schedules. Still, it is difficult to prepare a useful specification effectively. We want to propose an approach to creating a good specification. We started the work from scratch by determining what the scope of the specification should be. We asked people who work on IT projects what information is and should be included in the specifications with which they work. This paper presents results from a survey conducted with 163 participants who have experience working on commercial software development projects. The main observation is that the content of requirements specification differs with respect to project characteristics, such as industry or financing method. We also noticed that the information about integration with external systems and functionalities most often appears in the SRS.