A trace unit, diagnostic apparatus and data processing apparatus are provided for tracing of conditional instructions. The data processing apparatus generates instruction observed indicators indicating execution of conditional instructions and result output indicators indicating output by the data processing apparatus of results of executing respective conditional instructions. The instruction observed indicators and result output indicators are received by a trace unit that is configured to output conditional instruction trace data items and independently output conditional result trace data items enabling separate trace analysis of conditional instructions and corresponding conditional results by a diagnostic apparatus. The instruction observed indicator is received at the trace unit in a first processing cycle of the data processing apparatus whilst result output indicator is received at in a second different processing cycle.