Motivation, self-efficacy in learning and practising alongside particular personality traits are the main factors which influence the piano students' music achievement. Research and definition of the prognostic indicators related to the music development, musical instrument learning objectives and music achievement present a challenge for music psychology experts, pedagogues and instrumental pedagogy teachers. The relevance of this research has been recognised in many primary, secondary and tertiary education institutions in European countries and worldwide whereas the Croatian context still does not pay enough attention to these questions and topics, and not much research is recorded on this subject. Therefore, this thesis presents a scientific contribution to the study of music achievement and subjective well-being of the piano students in music school and music academies in the Republic of Croatia, and also clarifies and broadens the knowledge applicable in both music-pedagogy practise and piano methodology which is of a significant importance for the primary and secondary music school and music academy piano teachers. This thesis examines the prognostic role of motivation, self-efficacy and personality traits in predicting music achievement and subjective well-being of the piano students on the subsamples of the piano students (N=215) and (N=92) taken from the five largest Croatian music schools in Zagreb, Split and Rijeka as well as from all four music academies in Croatia (Zagreb, Split, Osijek and Pula). The theoretical part of the thesis contains the review of the fundamental concepts related to motivation and subjective well-being in music education. Motivation theories, education psychology and music education motivation models as well as personality traits and their impact on motivation and music achievement have been outlined. Musicians' motivation has been studied in the context of the self-determination theory and self-efficacy concept with the special emphasis on the application of these theory models in the piano learning process. The relation between subjective well-being and music engagement has been studied in depth. The following questionnaries have been used in the research: a) General Data Questionnaire comprising the questions related to socio-demographic characteristics of the participants and their parents as well as the achievement-related questions, exam grades and competition awards, 199 b) Perceived Parental Support Scale, c) International Personality Item Pool-IPIP, Goldberg 1999), d) Self-Efficacy Questionnaire developed for the purposes of this research according to the Guide for Constructing Self-Efficacy Scales A. Bandure (2001), e) adapted version of the Academic Motivation Scale (AMS-C28, Vallerand, Pelletier, Blais et al, 1992. f) Basic Needs Satisfaction in General Scale, BNSG-S which measures the satisfaction of the basic psychological needs (competency, relatedness and autonomy) g) Subjective Happiness Scale (Lyubomirski and Lepper, 1999) The results have shown that the students who are less emotionally stable, more amiable, conscientious, open to new experiences with a stronger parental support are also characterised as more intrinsically motivated. Personality traits have proved to be predicative for extrinsic motivation as well meaning that the less emotionally stable, more amiable and conscientious students whose family member is a professional and/or amateur musician are perceived to be more extrinsically motivated. Lower level of conscientiousness and insubstantial parental support are seen as important amotivation predictors whereas age, conscientiousness, intellect, father's education and parental support have proved to be significant self-efficacy predictors. It is possible to predict piano achievement on the basis of introversion, conscientiousness, musicians in the family, intrinsic motivation and self-efficacy. Interestingly, a higher level of academic success obtained in a music school/academy is realised by the students who do not have a musician in the family, have stronger parental support, are more intrinsically motivated and see themselves as self-efficient. Of all included variables, older age and higher father's education level are the sole predictors of participation where the participation in public performance is typical of older participants with a higher father's education level who have had a stronger parental support and an increased perceived self-efficacy. Personality traits – emotional stability, extraversion and amiability have proved to be compelling in predicting the subjective happiness. Different variables such as younger age, lower amotivation level and increased perceived self-efficacy related to the need for autonomy contribute to the satisfaction of the participants' psychological needs; self-efficacy, intrinsic motivation and intellect contribute to the need for competence, and younger age, greater amiability and lower amotivation contribute to the need for relatedness. 200 Obtained results, learnings and conclusions on the predictors of piano achievement and students' well-being make a notable contribution to the music-pedagogy practise and instrumental pedagogy, and also provide all the participants in the teaching process with new suggestions and ideas with a view to improving and modernising the piano pedagogy and methodology. This research can also be considered as a good starting point for the upocoming research whose objective is the search for scientifically-based models related to the prediction of music achievement and well-being of music students.