Abstract Directional drilling has become more critical than ever in the petroleum industry due to continuous development in offshore deepwater fields, environmentally sensitive areas and locations with restricted surface access. In addition to the significant increase in re-entries operations to extend the lifetime of onshore and offshore production facilities and on horizontal completion of wells to improve production rates and to have an ultimate recovery. The involvement of extra tools, expertise and processes make directional wells way more expensive than vertical wells, therefore, any moderate improvement in drilling process or tools selection could bring significant cost-effective results especially for offshore fields. However, the improvement is not an easy task, due to the complexity associated with directional wells. Nevertheless, it could be achieved by deeply analyzing directional drilling data in order to precisely determine the areas of improvement and to select cost effective tools. From this perspective, the ultimate goal of this thesis is to develop a comprehensive workflow which can be used to evaluate and compare the performances of commonly used directional drilling control tools and to propose the best tool in term of low cost and high performance. At first part of this thesis two topics will be discussed, the pros and cons of most used deviation technologies and the working principles of Rotary Steerable System. In the second part methodology overview of the developed workflow is explained in details. Briefly, the developed workflow consists of four phases, data gathering phases, in which pertinent data of highly deviated wells are collected. Since data quality and validation always have a significant impact on final results, therefore, in the second phase the predetermined data is certificated. In the third phase, Landmark software is used to process the data. Finally, by using specific key performance indicators (KPIs) and weighted decision matrix tool, the performance of different directional control techniques are compared and ranked. The third part of this thesis is specified as a case study, where the real data from Iranian field is analyzed by using the sequential steps of the developed workflow. The main purpose of conducting the case study was to evaluate and determine the shortcomings of the developed workflow. The final results of the case study reveal that the workflow is reliable and easy to use.