Progress in the last several decades, show that there have been increasing discussions in policy making and academic circumstances of the respective roles of public and private investment on economic growth. This research attempts to analyze the influence of private investment growth, public investment growth and also the influence of population growth on economic growth (stated as PDRB per capita growth) in the city of Semarang during the periode of 1992 – 2006. The data used in this study are time series data which are obtained from several references published by Bureau of Statistic Semarang, Central Java and from its Central Office in Jakarta and also other related sources. The econometric model in this research is estimated using Ordinary Least Square (OLS) methode and examined in terms of goodness of fit, F-test, t-test, and diagnostic test. The result shows that during the examined periode both private and public investment growth have significantly and positively effected the growth of income percapita. On the other hand, population growth has significantly and negatively influenced the growth of income per capita. Recommendation given by this research is Semarang City Government have to implement a regulation/policy that could stimulate private investment growth, such as simplify the investment approval procedure. On the other hand, they have to identify accurately kind of investments that produce highest net return and compliment the private investments, such as infrastructure construction.