Understanding the relationship between diameter breast height (dbh), tree height and volume helps in optimizing log selection for different purposes based on required timber volume. The purpose of the study was to create a modified model for diameter breast height, tree height and volume for Pinus caribaea to adequately fit all relevant variations in the data using R programme. Dbh is better predictor variable compared to tree height when volume is considered as a response variable. But this alone could not meet the assumptions of linear regression model. This therefore prompted the use of all data collected where by the tree height was considered as random effect. This was useful in the fitting of all data of the collected variables to a more useful relation in estimation of their linear regression relationship. The accuracy of this model was improved by addition of log function. Data of Pinus caribaea tree volume, dbh and height was collected. One hundred (100) trees were sampled in 1 hectare of pinus plantation with a range of corresponding tree dbh and height across the plantation in to a data set known as “mypinedata”. We wanted to know how dhb and height of Pinus caribaea as predictor variables affected its volume as a response variable. Comparison of dbh and height for best predictor variable for volume as a response in the linear regression model showed dbh as a preferred variable. However to meet the assumptions the linear relationship of volume, dbh and height was modified to fit all relevant data to improve on the model. The modified model for dbh- volume linear relationship was consequently created to cater for the adequate fit of the data or relevant variations using height as a random effect. Therefore modified model proved better fit for volume, dbh and height relationship in Pinus caribaea stand as deduced from its data summary and the assumptions when the log function was added. The assumptions for the modified model were met for the plot of residua