Background:
Onko Application is a continuation of the project of the Institute for Oncology and Radiology of Serbia - "Knowledge Against Cancer" (2015, 2017) encompassing the educational material for cancer patients (22 brochures) which contains information and answers to the frequent patients' questions. It is sponsored by the Ministry of Health of Serbia. The educational material, which also includes smoking cessation content, is adapted for mobile-phone use via an application. The app was published on Google Play Store in June 2019 and on the App Store in February 2020. The application isfree and in the Serbian language.

Objectives:
The goal of "Knowledge AgainstCancer" was to prepare brochures that are science-based, easily understandable, and which provide answers to numerous questions of patients, their families, and the general population about cancer, its treatment, and smoking cessation support.

Methods:
Analysis of reports on app downloads andusage statistics of the Onko Applications.

Results:
The application currently has about 1300 active users (2000 downloads since the publication), 406 of which are registered users (both sexes, average age of 44 years). The Smoking Cessation Brochure in Oncology Patients has 639 views and has received the top mark on a 1-5 scale.
Survey completion is enabled only to registered users, and the survey has been completed by 3.5% of registered users, all of whom are female and predominantly highly educated. The results of the survey have shown that The Smoking Cessation Brochure is useful, its content is appropriate, the text is clear, and that it provides answers to practical questions.

Conclusions:
The creation of this applicationenables greater access to information in the field of cancer prevention, treatment, and smoking cessation support, thus improving the quality of services provided to oncology patients and affecting the decision towards smoking cessation and inclusion in clinical treatment.